I disagree. Everyone has a role they're best at or preferred. Generally speaking, I find most the people who say that they can "fill" are equally terrible at all roles; most the "I can fill" players still have their preferred roles. They're just okay with playing something else. They're still specialized.
If you don't get to play the role you know, sure, you need to learn something else instead of "TOP OR FEED" or whatever. But there's no harm in knowing one role better than the rest. In fact, that's the best way to win. It's the same logic behind playing mostly one champion.
you guys seem to be talking about two different things, like differing degrees of specialization.
there is definitely no harm in knowing one role better than the rest (I wouldn't say it's the best way to win, which is what I think essentially this argument is about), but I'm pretty sure what Ferrio is addressing is this state of panic people get into when they are shoved into something they aren't comfortable with. basically to be a team player, you need to understand how roles function and how these roles are enacted.
but having something you can describe as within your comfort zone, something that you are particularly good at shouldn't be something looked down upon, it's pretty natural I think. it's more about this invisible line where specialization can either hinder or enhance your play.
so Ferrio, I think, is in the end talking about an aspect of the community that's pretty bad, where if someone doesn't get their ideal role the team is hurt in an almost inexcusable way; the outcome of the game and the prevailing mood of the game has been decided at champ select. that really shouldn't be how the game works. like a few months back TSM was winning a bunch of scrims where their players played roles they don't usually play, that's probably a better team quality than someone like Best Riven NA who is really good at Riven, or SilSol who can basically forward only one way of playing and manipulate solo q and be high ELO because of it. And obviously TSM has preferred roles to an extent (Xpecial being probably better at mid, but being the best fit in the team for support, for example, or Oddone playing jungle because he doesn't know how to CS well), but flexibility will always be a quality that's better in a team game and a quality that helps you flesh out how the game works.
it's more about one's approach I think. invariably you will be better at one thing than another. but will you focus on one thing to the extent that it becomes a detriment? will you play Kayle every game (shoutouts to TellYourself)? will you have this fleshed out idea that you are better at X, so if you don't do X some invisible percentage chance of winning the game will diminish? that's not really how the game works, there's a lot more going on. basically it's a good idea to be confident enough to know that you will adequately provide for the team in whatever role the team needs
disclaimerz: I'm speaking pretty hypothetically and not trying to attribute some of the attitudes that I have basically theorized to real life pplz