I see... So this is one thing the WN handled better than the LN.
In the WN the heroes weren't given this chance to improve, they were left to their own devices and suffered a lot. They did learn from the event however.
In here though, they did recieve some guidance, but they gave up. It may make sense for the spear hero who is reckless and Itsuki who's a selfish brat, but what happened here pretty much makes no sense for the sword hero. The sword hero is the youngest, and therefore he's immature, but he is still rational and aknowledges his mistakes. I can't see how he would react the same way as Motoyasu and Itsuki this time around, specially when they had just proven that the heroes a lacking. IT makes no sense for him tonot go through with the training, it's simply not in his character to do this.