It changes depending on the altitude difference in the scenery. These might be realistic or not, it really depends.
There are some sceneries we found (even default) where the parking *itself* is visibly sloped, I think pushback there wouldn't even be allowed from that position in real life, if the slope were really like that, surely a towbar would break, and I have no idea what will happen with the towbarless arms either. I guess that, at least from the parking stands to the typical pushback positions for that area, the apron should be reasonably flat, but the problem is in MSFS almost invariably isn't.