If Grealish had off field issues, he wouldn’t have been in the squad. See Phillips, Cancelo, Mendy etc.
He wasn't always in the squad and was benched a fair bit. Each situation is different - Mendy is a strange example to cite as he was arrested in November 2020, played games after and was still in the squad until he was charged in August 2021. Aside from anything else, his lifestyle choices were hardly the most professional, were known and he was still part of the squad.