Some horses don't like the feel of the grass reins as they bend, The Daisy Rein, from what I have seen, does not intefere with bend.
We had a horse who was a total nightmare with snatching grass, one day he just charged for the verge, got a mouthfull of grass and a dog turd all in one effort. You can imagine the stae of his bit and mouth. I am not tickle stomched, but even I was bowking!