I am aware! There is a note about it on the info page. Most of them work fine, but the 2x2 storage tank cannot be flipped in any direction. The problem isn't that it hasn't been enabled, but that the graphics required for flipped variants don't exist! Since I didn't make the original 3d models, this is difficult for me to do anything about.
In case you are wondering: Simply mirroring the graphics won't work, because the illumination and self-shadows are going to look all wrong. I can't make a kitbash either, because there just isn't enough visual information to be scavenged and put together like that. I would also have to create new shadows.
So this is a problem that isn't likely to be fixed, I'm afraid.
