People are using terraforming as an excuse. Gravity is a result of Mass. The moon is the same size. Same density. So, the only explanation (that I can think of) is that Guardian Suits have a flexible mass, so as to always apply 1G (Normal Earth Gravity Effects) on the body. This would prevent bone and muscle loss, as is common with in-space conditions. By flexible mass, I mean that they can weigh more or less, depending on environment. Ghosts would obviously regulate this, making sure that you don't float away or plummet through the Moon's crust.