In this case Google provided a reason - a ToS violation. If you want to get in the details ( action X on date Y violates ToS section Z), that might be pretty useful to bots and spam accounts ( know which actions get caught and what to avoid), which are probably the vast majority of what is getting banned.
When the ToS are 15 pages long this is about as useful as hearing "You're being arrested for breaking the law" when you're in the back of a cop car. Doesn't really narrow it down and provides you no way of actually defending yourself.
I agree that being too specific can help bots but the current way of handling these things is obviously flawed.
I agree that currently, "you violated the ToS" is legally enough reason and enough information. I don't think it should be.
I also don't think we want the fight against bots and spam to justify taking inscrutable actions against real customers.
Can't check other countries since Google automatically adjusts the country version to your location but you can check yours here: https://policies.google.com/terms
//edit: but you're correct considering this doesn't contain any service-specific ToS.