Users don't notice a deprecation warning. But they might notice adding a "time.sleep(10)" immediately at the top of the function. And that gives them one last grace period to change out their software before it breaks-breaks.
A breaking change causes a full-stop to a service.
An intentional slowdown lets the service continue to operate at degraded performance.
I concur that it's less clear for debugging purposes (although any reasonable debugging infrastructure should allow you to break and see what function you're in when the program hangs; definitely not as clear as the program crashing because the called function is gone, however).
From the article:
"We still received feedback from users that this removal was unexpected and was breaking dependent libraries."
I think we may be assuming different floors on service maintainer competency; with so many users pulling in dependencies across an arbitrarily-wide version window with no testing, such changes do break services.