I don't care for hyperbole much, but that version of Stairway, in context, is about as good as it gets in terms of interpretive musical performance.
Plant has talked about the reaction and in typical Plant fashion, "it's complicated"; I don't think it was the song itself, but rather the fact that what they created has spanned generations, and to see their friend's son doing that work justice... it's a beautiful moment, and historically, Heart has serviced the Led Zeppelin material with the proper mix of reverence and extrapolation. The main mistake - IMO -- of Zeppelin covers is that they play it too literal and too note-for-note. The beauty and magic of Zeppelin when they played live was that it was fluid, it was interpretive, it was all based on feel, primarily the ebb and flow of the interplay of Page and Bonham. That was the special sauce. IMO, Heart has done the best job of balancing that (though I've remarked that Matt Cameron nailed that essence in the live version of "Achilles Last Stand" at the Temple Of The Dog show I saw at MSG.