I obviously don't know, but I could easily imagine that Apples legal team has flagged it as a potential risk and the cost of keep the certification up to date is minimal, compared to some imagined risk. Safer to pay the fee, and not having to worry about someone at Apple accidentally calling macOS a Unix system in public.

Also, Apple is a huge company, there's the question of who's going to make the call the not update a certification that's negligible within the scope of macOS development. Better to not be that person and just rubberstamp the invoice from The Open Group. If management disagree, they can make the call, but they won't because the cost is to small for them to deal with.

The cost isn't negligible. The OS team at Apple is smaller than you'd think and has a tight schedule that cannot ever miss a ship date. Basically anything that uses anyone's attention has to be important.

> there's the question of who's going to make the call the not update a certification that's negligible within the scope of macOS development.

And one way that's managed is to have a DRI system which (ideally) prevents this from happening.