I know folks don't view this terminology in its traditional sense, but by contract law if the promise cannot be accepted and made binding immediately, it is not an "offer." For a promise to be an "offer," it must create a power of acceptance permitting the offeree, by his acceptance, to transform the promise into a binding, contractual obligation.
In the NCAA scholarship setting, the "offer" is the paperwork that accompanies the NLI form that is sent to the prospect. Everything else is just a promise, which is free to be broken at the whim of the promisee and with no legal recourse.
So, in essense, @ecdawg is right.