Right. Of course turning off forced inlining will speed up compilation. The article is completely silent about what it does to run time.

This is an unusual case, in that it involves code with SIMD instructions. Out of line calls usually mean the arguments have to be put on the stack, then loaded into the SIMD registers. Inlining opens up the optimization possibility of not doing that.

It's not clear what he's writing, but from the math it sounds like a physics engine for animation or games.