I love using a pasta pot/steamer where there is an inner "colander" pot so that you can pull all the pasta out easily.
BUT... in all of the ones I've seen, the inner colander doesn't go all the way to the bottom. There is a gap of about 1.5 to 2", plus the 1/4 space of the bottom of colander itself.
The means I have to boil a LOT more water. That takes more time, uses more water and energy.
It seems like a gap of just 1/2" or so would be sufficient to "insulate" the bottom of the pasta from the hot bottom of the pan. (And I've boiled pasta for years without a colander inside (so zero gap) fine).