Yea, I don't think that the case here. The 120V in the garage is part of the "exterior lighting" circuit so it's not dedicated. Even if it were dedicated, I'm pretty sure they used 14 gauge for the 15 amp circuit because it's cheaper. The unit was built only a few years ago. On the plus side, there is space in the breaker box for an additional breaker if needed.
The biggest problem is the running of the wiring out to the detached garage {grown}. The panel is on the 2nd floor in the laundry room so they would need to run the wire up into the attic, out to the soffit, down the side of the unit, into a ditch for about 25 feet, back up and into the garage. It would be a lot of work, and as you can imagine, cost prohibitive.