Ah, fair enough :-)

This does highlight a wider difficulty around effectively mapping floor numbers, heights and separate parts of buildings that are on uneven/sloping ground though. Technically the way you mention, relative to ground level on the north side (entrance side), would have height=0, or perhaps height=-3 or something as it is a basement level. Meanwhile, where it sits on the south side, the ground level is much lower, so in reality it's more than a metre proud of the surrounding ground. I think my height=1 was a compromise to demonstrate the distinctive shape to the building (part). It's a difficult thing to standardise really.

Another nearby example is https://www.openstreetmap.org/way/148653738 which has an underground level which becomes ground level at one end of the building.