No, this is defninitely not a bug.
I'll take Donny Manaf as an example:
Week 1: 82 minutes
Week 2: 90 minutes
Week 3: 67 minutes
I don't know why you think he has to pop to proficient? You have to be happy that he's still on respectable!
Assuming that 50-65 minutes per week is perfect for GS, it's better to give his manager some more advise about managing minutes ;-)
When I run into an invisible spider web, I instantly become a kung-fu master.