I've been enough on the insides of these kind of decisions in the past to know that it's very much lawyer and PR-driven, and that the right thing to do from tho

I've been enough on the insides of these kind of decisions in the past to know that it's very much lawyer and PR-driven, and that the right thing to do from those perspectives is to terminate the relationship as quickly as possible. If you give lots of lead time then you're just creating a festering sore for yourself and giving the other party time to mobilize against you. It's better for it to be a fait accompli with minimal notice given, so that the other party immediately focuses on moving on rather than trying to mobilize to reverse the decision. It's definitely not good for the company caught on the receiving end of such a decision, of course, but the hosting company is optimizing for themselves, as all companies are inherently selfish. And given how much racist garbage Ruqqus is hosting, I don't think Heroku cares too much about any hardship incurred.