It depends on when the seed is generated, as I said in my edit while you were replying I guess.
If the seed is generated at the time of purchase (so when he locks it in), then I'd say he has a case, because he had a set of winning numbers generated by a random seed during the eligibility window and a ticket purchased during the eligibility window for this draw.
If the seed is generated at any other time (er, I should say, at the time of printing -- since there'd still be a window otherwise), he has no case, because both the ticket and his winning numbers were generated during the eligibility for the following draw, regardless of when the purchase itself was made.