You know, if I was providing support, I'd consider it a point to make it as easy for customers as possible to know what to do. Like if I banned them I'd include how to appeal/fix and how to get more info.
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.
Do schools or parents not teach philosophy or ethics to these FAANG employees?
You haven't been to school this century, have you.
Also at minimum I'd think I'd allow them access to past emails as a default.