Though I'm not sure why it wasn't broken in vanilla, none of the meshes had "NCO" (no collisions) in the nifstringextradata so I added it and now it works perfectly (though obviously with no swaying). Someone should make a nexus page for OpenMW related mod fixes, if you do feel free to include this and let me know if you need any bumpmapped models fixed because I probably already did it.
Does this have the same problem as the regular grass mod in that it is hard to click things located underneath the grass? I've been using the normal grass mod by Vality, LizTail, et al, but I would definitely like to give this a spin at some point.
Though I'm not sure why it wasn't broken in vanilla,
Well, I'm not sure if I understood you correctly, but, I think, the mod is actually broken in vanilla, so to say. That seems to be intentional, though.
The point is that the mod mustn't be activated in the vanilla game either but should just be "fed" to MGE XE.
Secondly, my browser informs me that the file contains a virus or malware.