What did Adam know about the K2-Phantoms?
Well, not much at all. He had seen Tron use his ability once when he was still a K2-Phantom.
Also, Adam had fought Prago, a real K2-Phantom, but at the time Prago was at his worst morally.
Physically he was a K2-Phantom, but inside he was getting weaker by the day as he continued to rot from the inside because of his fears. The defeat brought him to his senses, but he couldn't demonstrate all that K2-Phantom was capable of. Well, that was why he had lost that day.
The K2-Phantoms had to fight against the Yellow Threat Monsters and travel to distant territories that even with the SH-01 fighter, would take quite a while to reach.
And, to do that, they needed decent combat power.
Not everyone was as capable as Adam as a K1-Phantom to fight against Light Yellow Monsters and win. Many K1-Phantoms became K2-Phantoms as soon as they had the opportunity.