Awake physics but only certain bones?

No. The answer is to make a proper profile and swap the profile instead of coding individual chains.

But 8 years ago that wasn’t a thing (and the chain was first a thing around 6 years ago, so they didn’t even have that option).

And even now a days - with chaos - who knows what factually works.
Pretty much nothing actually, particularly if you look at performance differentials between Nvidia’s PhysX and the mess epic made with their own concoction…