Isn't that what should be expected?

Well, for mob heads if it's disabled you can get heads via charged creepers. Shouldn't be the same for players?

But that's also a vanilla mechanic. Idk, I can see it being both ways

I mean for consistency make player heads like mob heads. By default they'll drop if a charged creeper kills them, but you can enable "Headcrumb Player heads drop randomly" to get them randomly on player kill.