by Thorsten » Tue Jan 26, 2016 3:03 pm
They do, but random vegetation is an effect declared on top of that and effects do not support the standard conditions (they do support predicates). Since grass runs over what is in essence the normal tree effect, disabling it when Rembrandt is running kills all the trees.
I suppose with enough determination it can be hacked into something that actually switches, but then it's also a performance-critical thing,...