[centizen]

It certainly seems valid, but in context of all of the other protections it's difficult to say for sure if is or not.

But considering it either hasn't been used in other games, or at least infrequently enough this emulators author has never seen it before, I'm leaning towards it being another protection.

[ianferrel]

Or they upgraded their compiler/enabled more optimization.

Combining sequential writes into an STM is a standard optimization.