If you already have those 10 years of bussiness data on Microsoft or Google services or their respective clouds, are you feeling safe?

I'm not a lawyer but technically most if not all cloud providers, specific to AI ("neo-cloud") or not, to provide Customer-managed encryption keys (CMEK) as someone else pointed out.

That being said if I were to be in such a situation, and if somehow the guarantees wouldn't be enough then I'd definitely expect to have the budget to build my own data center with GB300 or TPUs. I can't imagine that running it on a Mac Studio.

People store that data in databases in the same data centre so it's really the same level of trust needed that your provider adheres to the no training on your data. Trust and lawyers.