He doesn't have to sign a NLI if he doesn't want to. The NLI is a binding contract but it only binds the kid to the school. The school can recruit over the kid before he enrolls (like in Okpomo's case) or a kid could sign in November only to see the Coach get fired at the end of the season or take a better job. Heck, a school could tell a kid that he/she should ask for a release from their NLI (**** move but a school could).
I'd never let my kid sign a NLI. Some schools **** around, especially when they fire a Coach, and delay granting the release because the school wants the incoming kids to wait and see who they hire and at least talk to that Coach, blah, blag, blah.
Okpomo can sign sign financial aid papers with the Wake Forest and he is good to go.