That's kind of the flipside of what OP is describing. OP is saying if it's colder outside than inside, and you want it to be colder inside, the unit would intelligently just pull in unprocessed (except filtering) outside air.

An HRV or ERV is designed to pull in fresh air without losing heat from inside (or while keeping the heat outside in the summer), by transferring heat between the air being drawn in and that being exhausted.

Yes - these are necessary in houses designed to minimise air leakage, because without them they can end up so well sealed that they do not allow enough air changes per hour.