Depends if your new to pinning or not. I've run 400 with no pain as Im sure many have. Pain is not indication of purity. That could just come down to the individual, how much they pin, and what muscles they're pinning.
I agree most 400 test hurts but I'm not sure it's due to the oil crystalizing in the muscle. I think that's more of how it feels than what is actually happening. Like the other posts say it's more of what it's made with to get the product in suspension like BA.
I also feel like test 400 is just expensive test since so many guys sell 250/300mg test that works great.
Anyway to answer your question you really can't tell if it's underdosed by pain. Even if it is if he eats right and trains right he's gonna make progress
I’m very sensitive to pip. Even with pharmacy T200. Toro has Test E 400 and I never once experienced pip. I know it was dosed properly. Im currently running Omni’s Test C 250. I experience occasional minimal pip and it’s made with miglyol but I can pull and push with 30g so it’s worth it.