Sure, they fit. And if the 1971 fenders don't have the fender gills (a 1971-only premium option) they will look identical to the 1970 fender. In 1971, the front fenders came in two versions.
But I am a little fuzzy where it comes to the headlight end pieces of the grille. Because they screw into the fender sheet metal, I don't recall if those holes are the same location on a 1971 fender. There could be other differences I'm unaware of.
When you go look at aftermarket fenders, they do indeed list two different fenders for 1971, with, or without gills. I would expect if the 1971 standard fender were an identical replacement to the 1970 fender, they would be listed that way on their websites, and on the 2-3 websites I looked at, they are listed (the 1970 and 1971 standard fender) separately - as if they are indeed different products.