No support for 8 bone weights per vertex in BONE_INDICES and BONE_WEIGHTS in vertex shaders?

[BunkWire2X8]

I noticed when looking up vertex shader systems, I come across these two rather useful looking shader built-ins:

...but like, what happens if the model is using 8 bone weights per vertex? Does it just cut off or something when you try to use these?

Looking it up in the source (with my questionable analysis skills), I can't seem to find any code that attempts to consolidate 8 bone weights into vec4 built-ins, so I am kind of left with assuming that the data would just cut off there. Some clarification would be nice though.

Also, would it be out of the question to add BONE_INDICES_2 and BONE_WEIGHTS_2 built-ins for when 8 bone weights are used in a model? (assuming that the above analysis is correct) I figured that would be an appropriate solution, assuming that implementing something like this wouldn't be held back by some kind of technical limitation.