Apparently that is the way it is done?? Though the house I grew up in was one level over a crawl space. The furnace was in the attic and the vents in the ceiling.We have floor vents.
This house has floor vents for the hot air on the first floor (over a crawl space) but wall vents upstairs because there is no space between the first and second floors. The subfloor of the second floor is the ceiling of the first floor. I think I would prefer the low wall vents for the hot air, no chance of dropping stuff down the vents! The return vents are low on the walls.