Some of the toilets I lived with in Germany had almost no standing water in them, and the waste ended up on a ledge. The flush valve had a large volume that washed it off. I didn't particularly like it, but it was what was in my apartment, and was seen elsewhere.
The gravity flush, wall-hung toilets' water surface area and depth is mostly determined by how much water it uses per flush. Unlike an old one from way back that might have two gallons or more in the bowl, when you only use 1.6g or less to flush, you need to be able to exchange ALL of the old water and then some, if you want to ensure a totally fresh supply, and not just some diluted crap from the last use. So, the water spots and depth are smaller on all of the new toilets. Some compromise depth with area, assuming whatever lands there won't be very thick or piled too high. Some are fairly deep, but don't cover much area, with the possibility of the waste not hitting the water spot. This has nothing to do about it being a wall-hung toilet or not, it's a design consideration of the brand and model chosen.