There’s a back story on this.
When CK4 was still in its proposal phase, of PC11, Ford was one of the engine OEMs very unhappy with the proposed specs. Initially, FA4 was not proposed. It was going to be one standard, not a split standard. This standard was also initially proposed with a low phosphorus and zinc level. Capping it along the lines of PCEO products.
Mind you, this never happened. It became a split standard. And it had a wide variation in what was allowed in terms of formulation. However in the meanwhile, Ford developed WSS-M2C171-F1 standards.
When CK4 launched and Chevron / Delo / Oronite (thus others) went low phosphorus, it became a thing. And is still a thing. The very first generation of Rotella CK4 didn’t meet it. (This has since been changed of course.)
Ford also did not go to CK4 when it came out, for well over a year. Motorcraft 15w40 was still CJ4. And blended as CJ4. We did not get the change notice for a long while after. Mind you, this is an important line. My company is the largest motorcraft distributor in the U.S. we also literally wrote the National Motorcraft QC program for bulk oil, for motorcraft. So the change over procedure is important to me.
As for Mobil being in Ford stores… that makes ford very unhappy.