I think they go with what works rather than anything clever. Don't think of it as a hometile system but more a wau of abstracting x/y coordinates into something more vague just to find out if the object is on-screen. The 'tile' they belong to doesn't really have to be the same size as your graphical tile. e.g. Tilesize 32*32, object 'holder' 128*128. You only want to know if the object is in a tile that's on-screen then you can draw it with it's own x/y.