alright so what is the terminology then
if there is none or we dont know it how about:
"outer cap" to describe what i was saying "there's no way" about, and
"inner stem sleeve" to describe what i think might actually stop the key (and what you seem to be talking about)
a taller "outer cap" should do nothing, as it should not matter.
a taller "inner stem sleeve" that covers more of the stem should actually prevent the switch from fully going down, reducing the throw, but hopefully not TOO much...
in which case, a "shorter" "keycap" would provide
longer throw...
still extremely curious
EDIT and if the switch's internals actually stop the key, then any different results from the cap are purely placebo. your fingers might be starting out lower from the desk but they would move the same distance.
EDIT and i guess i should state all this science is concerning only the cherry switch. it might apply to more, but the BS works totally different and doesnt have all these parts my drawings illustrate.
forgot to mention earlier, look timw4mail's avatar:

which seems to show the BS equivalent of the "inner stem sleeve" preventing the key from going down further
EDIT this will sure be funny when he changes his avatar, and someone reads it later, trying to figure out what my argument has to do with a hot dog