Absolutely, but I'd argue that the first example in the book is not the best place to put this. Learners will at some point encounter pre-RSR texts (or personal communications that don't care about RSR or other standard language features), but much of what they are likely to encounter at the beginning will be newer texts that use the current conventions.
That was one of the goals of the spelling reform to make the use of ß more consistent and use simpler rules for it. Exactly because there is no difference in pronounciation between ss and ß.
So what I’m trying to say is that s/ss/ß have distinct use cases which follow consistent rules.
Cultural identity and pride in one's lingual heritage play a part too. As a Dutchman, I like the German ß. Nothing conveys the notion of a foreign country better than another language and a differing orthography.
The ß even has a proper capital these days: ẞ. While no word ever begins with ẞ, you do need it when capitalising a whole word — e.g., on a sign.
Nichts der Art.
"Einfluß" and "Zusammenfluß" have officially been spelled "Einfluss" and "Zusammenfluss" since the reform of 1996,
Which many adults I know continue to thumb their noses at, to this day (in personal communication, at least). In any case, arguably one needs to be aware of the pre-RSR spelling conventions to have a solid grip on the language as a whole. So I would prefer a reference that made us aware of both variants, actually.
As to feminine nouns -- good call. It's a difficult task to put together reference materials that are both comprehensive (and approachable) and obsessively accurate.