Not every fab use BSIM models. Philips (now NXP) use PSP models for their own fabs and implement them as verilog-a code. This is a physics based model instead of fitted model like BSIM.

TSMC has their own C-library on top of BSIM models for FinFETs because BSIM isn't covering what they need. I don't know what will they use for GAA stuff.