Are you saying in National Matches you can or cannot call correction?It's true, in national matches you can call correction. However, a lot of teams including ours share wind calls. Some of the less experienced guys share that wind in mils, or moa. It's easy to convert mils to moa, but if you do it in mph, then that's a conversation you don't want to be doing in match. Matches aren't the time to do math imo.
Also, I find that communicating in miles per hour is actually the best way to communicate as we may shooting different cartridges, different reticles, whatever.
If I'm shooting a 300 Win Mag with my MOA reticle, and I hold for a 5 mile an hour left wind and get a hit, and you take that information, and you're shooting a 308 with a Mil reticle, and you hold for whatever your 5 mph left for your 308 is, you're going to get a hit.
Communicating in miles per hour cuts through whether we're shooting different cartridges, different speeds, different reticles, you apply your own data.