Looks like you are using the classic interface?
I only see that with that legacy view
Check that. I followed your steps and can reproduce in the new interface as well. Yea, must be something new.
I dont see anything in the Roadmap. But I can also see this in the classic interface so maybe its bee their longer than I knew.
https://outlook.office.com/?path=/classic
Do you have this option in the upper right corner?