not true at all.

what if you want to have a big reverb on the snare, but the kick
completely dry?

what if you want to have the toms do a dramatic stereo pan during a
fill, with the hi toms gated, the low toms open, and have the snare
with huge reverb and be able to eq the kick differently, apply
compression to the kick, and have the kick be completely dry?

the truth is that more mics give you more mixing options. that's not
always what you need. but when you need it, there is no substitute
for the discrete mixing options that a multi-miced setup will give
you.

it's a nice thought to think that a singe cubic inch spot with a mono
or stereo mic can capture whatever you want depending on where you
place the mic. but it has nothing to do with reality. unless your
reality consists entirely of easy-listening and old big band music.