Hi again and thanks for your patience,
As the polygon geometries are encoded as a series of rings, the filled rings must have vertices in clockwise order, whereas the vertices of the holes must be counter-clockwise.
Also, the order of all the rings (filled ones and holes) matters: the FIRST ring is considered as filled, followed by N number of holes; then another filled ring and its holes should come, etc. This means that if the first filled ring's holes are ordered after the second filled ring, those won't take effect (see example here: https://codepen.io/gsoosalu/pen/jOXzjWR).
PS: also note that the poylgon geometries shouldn't have any overlapping edges, e.g. a hole's edge shouldn't intersect nor overlap a filled ring's edge.
Hope this explains a bit better how the geometries are currently interpreted in 3D.