There are many threads about this gimbal guards. So far, they are the possible suspects of some P4 crashes here. Even if you're P4 crash accidentally, and you have a gimbal guard installed, DJI won't cover you with the warranty. The thing is that the gimbal guard may interfere with the sonar system. If you want to see an example, check this video.
I have that exact part on mine. I only install it to use with my 360fly 4K. I've flown it a couple times with no issues at all. I don't install it unless I'm using 360 camera.
I believe DJi Ken started a thread warning P4 pilots to not use this device as it could and would cause a crash and using any gimbal guard that crosses between the landing gears would void the warranty on the P4.