How to block airflow under an interior door over carpet

I just finished our garage this past summer and here are a few things I did.

I insulated the garage door by cutting pieces of rigid insulation foam to fit into each piece of the garage door. You can glue them on and then seal the edges with expanding foam or caulk.

On the side of garage door I installed weather strips and also on the top/bottom of the door so that it is sealed when the door closes.

If you have any windows I would make sure to seal them (I boxed mine in with wood and then caulked). Also depending how you finished the bottom of the garage walls, I would seal the bottom (my drywall buts up right to the cement floor, so I sealed the space with expanding foam and cut the excess away).

It makes it easier for the carpet installer because they don't have the baseboards in the way when they're nailing in the tack strips next to the wall.

On the other hand, it makes things a little more difficult to install the baseboard later because the carpet and tack strips are in the way when you're trying to nail the baseboard to the sole plate in the wall. This is much more of an issue if you're nailing by hand than if you're using a brad nailer. (I've done it both ways; use a nailer.) If you're doing a long wall, it can make lining up the pieces of baseboard a little trickier because the tack strip and carpet can get in the way.

On the whole though, I'd follow his advice and use a nailer to install the trim.