First. Why would Legion guys be that far into NCR, frumentarii yes, soldiers no.
Second look at it, if it had the football pads you would see the chest part, you only see shoulders which appear to have a red color with words. and his huge belt and shorts, Legion doesn't have those.
Well, as for the first part, I seem to recall there being mention of a clash between NCR and Legion at the Divide, but no one returned and the Divide became a sort of 'DETOUR' from then on.
As to the second part, I noticed the shorts. I mean, in theory, one COULD argue that NCR and Legion remnants scavanged what they could to keep protected from the sand. I mean, I dont believe the Legion wear underwear under those tunics of theirs. But tbh, it's more than likely just a reskinned Legion Armor made to look scrappy and stuff, I dont care either way really :shrug: