Honestly I’m glad they highlighted the telemetry. I went through the local report about what’s included and while it’s not an upsetting level of detail, it’s more comprehensive than I would have opted in to if asked.
Still, as sibling points out it’s in a completely different league from slurping up your IMAP creds, something which has always been local-only data. This is the second time I know of recently where MS has trampled on this kind of local-only expectation - the other was Edge defaulting to sending the contents of textboxes you’re filling out on webpages to the MS cloud for spelling and grammar checks. Thunderbird is still a sound recommendation, and unlike Microsoft, I trust that if I uncheck the telemetry box they’re not going to try to get me some other way.