If you’re discharged from Marine DEP twice, can you still enlist and go to basic or is it against Corps policy?

My buddy was discharged from Marine Corps DEP because he failed to graduate high school on time. Because he had been in for almost a year, they discharged him and re-contracted him the next day, scheduling him to leave January 19th. However, it seems that he still might not graduate by that time and his recruiter told him that if he didn’t go to boot camp on the 19th, then he’d never go at all, stating that it was a against Marine Corps policy or something like that. Is it really against a policy or is this just some scare tactic to motivate him?