So I got it working.
A couple of things:
From the documentation:
ZitatTo improve performance, for simple constructions that do not contain ground faces, terrain alignments, edges or depot/station/industry/town building definitions, there is no construction placed in the game but just the seperate mdls. These can not be configured afterwards or be deleted all at once. Furthermore these types of assets do not support the
labelText
custom texts from constructions.
Note the last sentence.
Also, the array is zero-based, not one-based, so we need:
Further, we need to add one of the data types mentioned in the quote above, so that we get an actual construction on the map, rather than a bare model.