Are you both speaking of the same AR-10? I don’t doubt the recent ones, upscaled AR-15 clones are more dependable than Stoner’s version used by the Portuguese in their African colonies back in the day.
The ones originally made by Armalite and that served as the base for the AR-15 are the ones I’m talking about. The Portuguese liked them but most places that trialed them against the FAL had them turn out to be less reliable than the FAL.