Not sure about the amount of fuel needed to land, as there is much less atmosphere on Mars, and none on the Moon. I would still guess that it needs less fuel there as well.

But the other Starships don't and adding them would make a big difference.

Since you need a huge fuel tank in orbit that needs to be refilled by multiple starships to refuel Starship HLS to actually land on the moon adding legs on those refueling Starships would decrease payload capacity, and thus you'd need even more Starships to refuel the tank for a single lunar landing.