YES furnace REQUIRES minimum airflow so it won't overheat
Most mfg. can't be accused of over doing it......usually just install minimum.
We have one that is right in middle of kitchen floor where you are either standing on it or having it blow up your pant leg/dress.....woo hoo!
Craft store......bought a package of flexible magnetic sheets. Cut them just a bit oversized and place them over the register in kitchen. Throw rug went over the top of that.
Other registers were replaced when we first bought RV cause they were cheap stamped metal that broke when I walked on them. Bought decorative registers that can be opened/closed. We adjust (not fully close due to the closed/unused one in kitchen) to balance air flow.
Bathroom has round adjustable one in side of sink cabinet.
In summer when not needed we close and cover with the magnetic covers. Keeps stuff from falling inside them.