> and doing a quick search of the kernel source it's not actually used for anything I can't find it referenced outside of itself.

It's being used here: https://lxr.missinglinkelectronics.com/linux+v5.16/arch/x86/...

Whenever the kernel gets a "device not available" exception, and CONFIG_MATH_EMULATION is set (which is the case when the kernel is compiled for a 486SX), and the CPU does not have a real FPU, and the "emulation" flag on CR0 is set, it calls the FPU emulator.