I used to think like Matt, that he has a bit of a Mickey Walker-esque reputation built there for him. But nowadays I'm more inclined to think that he's well worthy of it based on what he accomplished at the weight and a bit of well-educated guesswork. Once he hit his peak at the weight, he only lost once and it was on a DQ. He beat some excellent fighters there. Baby Arizmendi, Rodolfo Casanova, Chalky Wright and Petey Sarron, among others. I'd wager that's as good as Walker's tenure at 147, because to me, that's two all-time great level guys, a very good fighter/puncher and the world champion. Damn good stuff. I'd consider his fight with Arizmendi to be a good indicator of what he'd be like at featherweight. It's only four pounds above the limit, it's the only footage to my knowledge of Hank before Ross, and it's vs another featherweight great. He lookrd brilliant, and used the same style he always did. I think we can safely say that Armstrong was really ****ing good there, as good as he was above. Better even, give that he was a consummate banger down there as well. He was the only man to KO Sarron, who had 150 fights. One of only two men to KO Benny Bass, who fought nearly everyone in his era, and had 250 fights. He KOed tough Tony Chavez twice. He also KOed granite chinned Chalky Wright. I'm positive he was a massive featherweight as well. He was a big guy for his lightweight title fights, and he was incredibly strong and a tough. At featherweight, I imagine all of this is amplified given that he was in with smaller guys. What he did at higher weights obviously is where the backbone to arguing it is, but he did enough at the weight where it's not just based on that. I think he's the best featherweight ever, head-to-head. If he was ranked around the tenth mark at the weight, I wouldn't complain - but he isn't on mine.
Minus the early career losses, it’s the same reason Duran is so highly regarded at Lightweight. Or really any fighter who accomplished a lot beyond their natural weight division. Pacquiao is another good example. People tend to see Armstrong as either a natural Featherweight or Lightweight (which is accurate), therefore they rank him highest there even though technically he accomplished a lot more at Welterweight.