This is just a conjecture:

If it is indeed abuse related (whether there was any abuse or Google's algorithm just decided there was some abuse) then telling the abuser what got them banned is counterproductive from Google's PoV. Same reason reddit does vote fudging.

This is a dangerous equivocation of the guilty with the innocent, and throws away completely the notion of "Better X Guilty Persons Escape than that One Innocent Suffer."

Do schools or parents not teach philosophy or ethics to these FAANG employees?

>Do schools [...] not teach

You haven't been to school this century, have you.

Not even this millennia.

In the previous one they used to teach that the singular form is "millenium".

Telling people what they did wrong so they can correct it is appropriate. You don't have to tell them how you detected it, and keeping them banned until they fix it is fine.

Also at minimum I'd think I'd allow them access to past emails as a default.

And if it's not abuse related a Google employee could just take a look at it and lift the automated ban if it was unwarranted. Too bad Google doesn't like having employees for anything that an AI can do with 50% success rate.

The culture of the people who make up these companies don't want to let anyone know what happened or let them appeal it, because they "know better" and are "in agreement" with unspoken rules such that adjudication would be "a waste of time." It's all about arrogance and fascist behavior towards users in the name of expediency and risk management. Unless someone is a celebrity, they're squished like a cockroach if they stumble into the "light" of algorithms or human review.