They do seem to enjoy nestling amongst the plants.I just started a community tank with female bettas and they spend a lot of time hidden away in the clumps of grass.At first I thought I had lost one because she stayed hidden for so long.
I had one that had been kept in a vase with a plant and he would just stay in the tangle of roots.Everyone thought he was sick but he just liked to hide in there.I wish I could see my females better.They get into the short grass clumps and disappear.For all I know they could be curled up with a good book