RLPL is made by the Cantarelli group, which owns St. Andrews. So, you're getting what essentially is a St. Andrews made suit (not sure if Cantarelli would consider it a St. Andrews made garment, or one made by Cantarelli -- who cares).
This is apparently the case, RLPL deals with the Cantarelli group instead of directly with Saint Andrew's, as I've seen a fair number of RLPL garments that were made in the Cantarelli factory instead of by Saint Andrew's. Same group, but it is worth mentioning that these are different factories, in different parts of Italy. A Cantarelli suit is not a Saint Andrew's suit, they are distinctly different. I like Cantarelli's product very much though, and have no problem with Ralph Lauren using them, as long as the final garments are appropriately priced (lower, by 40-50%.)