There have been tensions between the FIDE organization and top players like Carlsen since the latter have been promoting an alternative chess organization around Freestyle chess (aka Chesss960), which has slightly different rules.
I.e. this is less about "dress code enforcement" and it is more about "Carlsen is fed up with the FIDE organization in general".
Hikaru mentioned there had been drama between FIDE and himself about having cameras at the same tournament — and he felt FIDE refused to give him airtime on their streams. Hikaru also had drama with FIDE about the Freestyle league.
I think both happening at the same tournament, which they had threatened to boycott if FIDE didn’t permit them to also play Freestyle league, indicates this is political.