The crossing appears to be mapped correctly, the original question in this note (height of the kerbs) has also been answered (tagged on the node).

There are no footways here with `footway=crossing` because the rest of the sidewalks aren't drawn as separate ways. I don't know about conventions in other places, but as far as I know in Belgium it's customary to map crossings like this when sidewalks/footways aren't drawn as separate ways. When they are, it should go without saying that the crossing should also be mapped as a way.