Invalid Mario Blocks always use different textures

[NARbluebear]

When I put a Mario Block into my map, it always uses what I assume to be AGZFLR01, instead of whatever I specify it to be. This is a problem for numerous reasons:
1. Mario Blocks look out-of-place when observed in a level that isn't Aerial Garden
2. Even if it was AGZ, how would we know the difference between it and the walls/FOFs?
Below: GIF of the problem. On the right is a solid FOF, and on the left is a Mario Block.

 

[sphere]

https://wiki.srb2.org/wiki/Linedef_type_250

Mario Blocks actually use the lower and upper textures of their control linedef, depending on if the item inside is still present or already obtained.