Hi, in Archicad 21 for Windows (10 x64) associative labels don't show object's thickness.
I have already updated to the latest Library update (Library-21-INT-Update-4527-1.1) and some things have been corrected though the thickness is not displayed on the object's associative label.
In the attached files you will notice that objects are custom defined, but this really doesn't matter, the problem occurs with original EN Standard objects also.
Takis