The APS kinetic heads, outside of allowing for better penetration or performance for APCHEM shells, do little for actually interesting game mechanics. Chiefly, I feel as though purely kinetic rounds outside of sand are far too ineffective for anything other than hole punching. Integrating thump damage into the kinetic heads allows for a greater variety of applications for kinetic shells and allows for more variety for other shells as well.
Also, high caliber kinetics will actually feel like throwing huge lumps of metal at something instead of needles that end up just being shitty PAC or pierce lasers.