From the AAIB recent interim report:
Whilst this is considered to be the most likely cause of the engine roll backs on G‑YMMM, and is consistent with data from the incident to N862DA, it has not been possible, due to limitations in the available recorded data, to totally eliminate the possibility that a fuel restriction, from ice, formed elsewhere in the fuel system which, in addition to an FOHE restriction, contributed to the engine roll backs on G‑YMMM.
And:
Tests carried out by the engine manufacturer demonstrated that fluctuations in the P30 burner pressure, fuel flow and spool speeds, recorded on the FDR and QAR during the engine rollback on G‑YMMM, were generally more closely matched when a restriction was placed in the fuel feed pipe approximately 25 feet or more from the aircraft to strut interface.
It does seem that there is a lot more to learn here that may apply to other types of 777 or even other types of aircraft. It's nice to have a "quick fix" in redesigning the RR FCOC but it may only be fixing part of the problem...