Honestly I think they might have more useful data than Google, given Bing knows more or less that same as GoogleBot. Meta doesn't come close, unless you want your LLM to be purely conversational.
Microsoft does seem active in this, e.g. https://microsoft.github.io/presidio/
Moreover, that isn't even the problem here. Suppose your company has a trade secret. You know how to manufacture widgets more efficiently than your competitors. If Microsoft produces a model that will now tell your competitors your secret process that it learned from your internal emails, it's completely irrelevant whether they stripped the PII out of your emails first.
Unlike googles victims (individuals) corporations can and do fight back when someone plays it fast & loose with their confidential coms
They have all the data, and no one else even comes close.