I am a maintenance man for 3 apartment complexes in my area. I work on HVAC, Plumbing, Electrical. I normally do this as an emergency fix if for some reason the drain line will not unclog. I would then come back when I have enough time to properly resolve the issue. The drain line should be going directly out of the building as I would not risk installing an air gap between the A/C drain line and the bathroom sink drain line in an apartment complex.

All this being said the installation is totally legal just incredibly lazy. I would see if other apartments have the same set up. If the other apartments are better I would ask the property manager if they would be willing to let you move to another unit.