I'm not sure if the cadet salary stops once you "have the hours". Are you implying once you hit 1500 hours you then suddenly jump from cadet salary to Direct Entry salary? I was of the opinion the cadet salary (approx 5-8k less than the corresponding Direct Entry salary for each year) lasts for the duration of the loan repayment, i.e. 7 years. Simply because, after that you have nothing to lose by jumping ship and in order to keep you on they have to match your salary, where as before you were receiving an incentive by having the £1k towards loan repayment tax free and they could offer you a reduced salary.
This is why it's not a sponsorship at all, but those who get on to the scheme benefit from a training regime that is supposed to be the best. And the course still provides the best method of getting yourself a paid flying job with an airline at the end.