This is in no way a "fringe" belief. As you can see by this archbishop's statement (he is no "fringe tradcath") Catholic clergy take validity very, very seriously.
Now there some other cases recently concerning Baptism. There was a priest who, it turned out, was never baptized at all, and therefore had never been a priest. The Church officials had to release a statement and notify everyone who was affected (because he wouldn't have been able to celebrate the Eucharist, etc.) and of course the priest was baptized and then properly ordained.
Then in yet another case, there was a priest in Arizona (and apparently also a deacon in Michigan) who had performed baptisms for nigh on 20 years using an invalid formula. The formula was invalidated by his use of "we" instead of "I". That's right, it was the wrong pronoun and it made all the difference in the world. The bishop of Phoenix released a statement to inform everyone affected that their baptism was, in fact, invalid, and they'd need to have this ceremony repeated. However, the bishop of San Diego said it wasn't really a big deal and not to worry too much about it. So yes, there is some variance about this, and there are clerics who say it doesn't matter, but I'd say that the latter bishop is an outlier, because that attitude doesn't really comport with Catholic law and doctrine. In fact I think it's harmful to tell invalidly-baptized people that it doesn't matter, because in another diocese 20 years from now, it may really really matter.
The formulas and the definition of valid matter have been distilled down to very simple elegant definitions over the years. It is definitely not difficult, for example, to bake altar bread that meets the simple definition of validity, because it's very exclusive and simple. Likewise, the words in the formula can be very simple. The priest must say "I absolve you" in the Confessional (in some language) or it doesn't work! In fact, that's all he has to say! The priest must say "This is My Body... This is... My Blood" or it's not the Eucharist!
These rules seem oh so simple and uncomplicated, but it always seems like some ad libber can get in there and bollocks it up.
You can be a part of some other Catholicism that rejects Nehi Grape! That is, and I am not fucking with you about this, just fine.
I mean, can you imagine the turmoil and unrest in a Church that would happen if the faithful couldn't depend on the validity of our sacraments? Imagine if, at every Mass you attend, you have to second-guess the priest and peek at what kind of bread is being used, and whether that bread tastes like oil or sugar, and whether the priest is using proper wine, and many thousands of Catholics thrown into confusion about whether we had received the Body & Blood of Jesus or whether it had just been deliberately and cruelly simulated in front of us? Imagine the uproar that would occur! That is definitely something that Church officials don't want to deal with, because it shakes the foundations of the faith. No, validity is a very real concern for anyone who wishes to keep the peace among the faithful.
Regarding leavened bread: leavening altar bread in the Roman Rite is illicit but it will not be invalid matter. It is because our Eastern Catholic brethren very much use leavened bread, which if it's valid for one, it's valid for all. Likewise, a Byzantine Catholic priest using unleavened bread would be acting illicitly, and probably get in a lot of trouble just from his parishioners, but it would still be a valid Eucharist.
Now, personally I definitely have seen priests and even provinces of religious orders where validity and liceity perhaps did not matter much at all. I was part of a community that used glass "chalices" (illicit), they eschewed crazy things like chasubles, and they used "gender-neutral" pronouns for God. Now they usually did use real altar bread and real wine for the Eucharist, but I'm fairly sure I saw a home-baked loaf thing used once. The way they played around with the words of the liturgy was disturbing to me, and honestly I determined that several of those priests really did not believe in the True Presence with the reprehensible way they treated the Eucharistic elements, post-consecration.
And this may be the case with your Chicagoan priests: they don't believe in the Real Presence, so why does it matter if they attempt to consecrate unfermented grape juice? (By the way, just looking at Ritz Cracker ingredients online, I'd say they're also invalid, due to lots of sugars, salt, oils, soy lechitin, and other gross stuff -- not even fit for human consumption, I'd say.) I'd say it is very common for rank-and-file priests to not care much about their vocation or for the rights of the faithful. But the faithful have a right to a properly-celebrated, licit liturgy with valid matter, and Rome tends to uphold those rights, but bishops have a lot of ordinary power in their own dioceses, and so if the bishop is obstructive or drags his heels, then Rome may have a real difficult time championing the rights of the faithful.
The Church is not "some other Catholicism" that "rejects Nehi grape", I assure you that it is the other way around. No faithful Catholic in his right mind will tell you that unfermented grape soda can be valid matter for the Eucharist; it was simply the fact that you had a series of heretical priests, and they may have been given ample cover by their bishop. There is not "tradcath" radical hardlining here: it's just simple doctrine.
[0] https://www.questioningchristian.org/2004/10/troubling_incon...
[1] https://www.questioningchristian.org/2004/10/why_i_cant_acce...
[2] https://en.wikipedia.org/wiki/Christopher_Hitchens#Criticism...
(I think, but am not totally sure, that this is a fringe tradcath belief, and that for the overwhelming majority of Catholics (including the clergy), this doesn't matter at all; if you felt it counted, did it in good faith, &c, it counted.