It's virtually impossible to not hit your forearm assuming you are doing everything correctly. If you look at all the high level recurve comps, everyone has an an arm gaurd. The same is true for chest protectors.
Google videos of the World Champs or Oylmpics and you'll see what I mean.
Even if this were not the case, why risk it? You don't want to get hit by a bow string on a 44lb bow in the middle of a comp.
When I was shooting bows, if you did things properly, you wouldn't hit your forearm. The problem is if you blow chow and don't notch the arrow properly. Or the notch blows out. Or the arrow shatters when you let loose. Then the string will hit your arm. I got hit once with a 35lb bow. I don't want to get bit by a 60-70 lb bow string nohow no way.
The angle between your arrow and bow arm may have been too high.
The strongest position is when your arms and shoulders form a straight line (with your shoulders low). So the closer to parallel the line of the arrow is to this, the easier it is to hold.
Now, technically you are correct. If your release is perfectly clean there should be no problem. But in reality, there will be some degree of 'plucking' going on. Your fingers can't open fast enough. So the string actually vibrates a bit from side to side. I have seen some weird follow throughs that avoid this problem.
There are very few top recurve archers that shoot without a guard.
Google videos of the World Champs or Oylmpics and you'll see what I mean.
Even if this were not the case, why risk it? You don't want to get hit by a bow string on a 44lb bow in the middle of a comp.