I am talking about the fact that the new default email client on Windows will hand over all your email credentials to Microsoft. This has nothing to do with Gmail.

My bank isn't end to end encrypted either, but that doesn't mean it's suddenly ok for Microsoft (or any other company) to suddenly start MITMing my online banking connections.

I think the concern is that it copies the emails of your non-Microsoft accounts that you added to the Outlook app, over to Microsoft servers

Adding a bunch of middlemen that also see the data increases the risk.