Sorry about not deleting unnecessary stuff in the last post--

AM and FM behave the same as other signals in an IQ receiver and if
you use I or Q alone they have the same 6dB loss I mentioned. You can
receive and demodulate AM and FM using only I or Q alone, but just as
with other signals you need both I and Q together to be able to reject
the unwanted mixing sideband and to recover all the power from your
desired signal.

73,
Glenn