Inconsistent way in area

[mmd-osm]

Given the following query:

way["building"]({{bbox}}) -> .ways;
.ways out geom;
way["building"](area.ways);
out center;

My expectation would be that out center does not return a result for any of the buildings. Reason being, that the area boundary matches exactly the way, and there's no point inside the area. However, it seems that for some buildings, that's not the case, and we can see a center point nonetheless. Somehow this seems to be inconsistent.