The word you're looking for is "bimodal distribution".

The spectrum of sex characteristics is a bimodal distribution with two peaks. and the vast majority of all humans fall close to one of the two peaks peaks. however, they indeed exist medically classified circumstances for bodily sexual expression that is not on one of the peaks but somewhere in between.

and the percentage of those not close to the peaks is heavily contested and varies between 1 in 15000 ( putting extremely high bars on "uh wen can't tell") to 17 in 1000 (counting for example a larger clit as a penis-y ambiguous thing)

bimodal distribution with distinct peaks and a low but non-zero density between the peaks.