That is very possible as well. Like a hidden attribute that makes it easier to keep at GS 9 more often. Or a different "sweet spot" for minutes per week like you say.
Over my time it could be just co-incidence that my players that stay GS 9 longer have higher stamina. Small sample size for just my team vs. a big country's database.
If you remember me, then I don't care if everyone else forgets.
