Known issue that Apple needs to address because this would be a blocker for a lot of teams that depend on Testflight https://developer.apple.com/forums/thread/721534?page=2

Can confirm this is happening still - have tried the creating another group with un-checked the box " Enable Automatic Distribution" and that did not send a build to TestFlight - Have also tried the add "Test" under review notes which did not work either. Apple really needs to address this ASAP