It's ONLY a "concern" if one worries about Ford denying an engine internals warranty (as I am currently since I CANNOT afford to replace this engine). Not sure you were being facetious/sarcastic or not above.
Even though yes, they must prove beyond any doubt that your non-approved/certified oil (albeit possibly of even higher quality/standards/specs than their 'certified' oil) CAUSED the failure, but WHY give them any ammo, since a used oil analysis costs them much less than a new engine/install labor??
Otherwise (and once mine is out of drive/power train warranty) I would use the non-certified 'boutique' oils (Red Line, Motul 300V, Amsoil Signature Series, RP, JGD, Torco, Millers, etc.) in a heartbeat.