I think he's actually stating competition and heavy sparring are what would validate it here. I'm going to disagree though.
It would validate it to an extent, basically tell you "I'm better with this than the average joe", which is fine if that's what you want. But if the people you are training with don't know what they're doing and the person teaching you doesn't know what you're doing, having the 20 of you fight each other will only help so much. If you keep winning, you have no knowledge of whether you are good with that weapon, or if you're just better than 19 other people who also suck with the weapon.
It's similar to those schools that only fight in-house. They may very well have a lot of experience fighting, but than they go to compete elsewhere, and discover that their skills don't transfer outside of their particular dojo. What sucks is that for a lot of these weapons, there aren't enough people fighting with them (you have the dog brothers but thats about it AFAIK) so that you're almost forced to practice with the people you train with.