If it is that easy more players that don't like their draft position would hold out. It sounds good coming from the agent, but if you're a player would you find it easy to turn down 500K per year and go a full year with no pay? I would probably try holding out after playing a year when I had money in my bank account.
There is a really good chance that if he re-entered the draft that he would not be a 1st round pick anyway. Players lose their luster to teams when they have not played in a year.
It's a fascinating situation and I feel bad for the guy if he didn't do anything wrong. It will be interesting to see what happens.
If a team does draft him and he is contemplating not playing, they would likely offer to give him a new contract after the 1st year. The contracts are set for draft picks, but IIRC teams can give them a raise after the 1st year. Now you have this kid facing a choice of taking 500K per year and a verbal "promise" to give him a raise vs sitting out a year with zero pay. That's really hard to do unless he comes from an affluent family.
