Ya Microsoft lobbies for that, at our place too.

The reason is that copilot resells other people's models (they're just a middle man) and there's an easy way to cut them out. So they blow up the dangers of other people's AI. Whereas if your data is in M365 they have it all anyway whether you use copilot or not. So they're trying to build a moat so they don't easily get cut out.