So I just got a waiver to enlist in the Guard with 30%. I still have to take the flight physical, which is separate, before sitting for the board to hopefully get selected as a pilot.
From what I understand, the VA rating matters less than what your actual physical condition is. You still have to be honest about your history, and that still will be taken into account, but just having a rating doesn't necessarily mean that whatever the problem was is still there. My back and knee (which potentially still could pop up as a problem due to it being in my history for the flight physical) are fine now, but I still have a rating. I've told the VA as much as well. If they don't want to reduce my rating, I won't fight them on it as it shouldn't matter.
Where it did matter is MEPS required me to get a waiver to come up for a physical, and the Guard required me to get a waiver to enlist. Had I still been in the IRR, I may not have needed that.