They did not as far as I remember. They started with AP and APHE was unlocked. The difference was, before the pen formula update, AP had superior pen that meant you used that instead of APHE in some circumstances. The pen formula update just made AP pointless/something to get past like all the pointless versions of AP before getting APCBC.
As far as I remember APHE was never stock for USA. I always held both APHE and AP until said update, whereby after there was no longer any point due to minimal differences in pen. AP was only superior for pen, nothing else.
AP throwers had at least 3 versions (including stock) before the final decent shell was unlocked (though possibly skippable as not linked).