You can get away with them at 200 easy enough. At 300, there will be days when the wind will make you wish you were shooting 77s.
In terms of a 5 MPH full value cross wind at 300, you are close to 2.17 MOA with the Berger 52 @ 3100, and 1.26 MOA with a 75 @ 2750.
By itself, that doesn't cause an issue if you compensate for the windage, it becomes a matter of margin for your error.
If you miss a wind call, that can make the difference between putting many in the 9 ring versus just getting fewer Xs.
You should run some tests on a windy day at 300 just for the experience. That would show you why you hear this advice so often.