The problem with it is that it really only works if everyone knows what they are identifying as and has no real reason to misidentify.
Who has a reason to misidentify? And what does "misidentify" mean there? When an offshoot of RPGs colonized the idea space now known as story games, there's no nonarbitrary way to say whether they were RPGs or not. So when the authors of these story games, knowing their origins in RPGs, declared them RPGs, why should we argue?
It ends up really being just a hat to wear
I wasn't arguing that this necessarily works on a game by game case, but when a whole subgenre calls themself RPGs, then I'm hard put to say that they aren't.
So from my perspective either we need to decide RPGs have a definition other that self-identification, or we just need to recognize the term has no meaning and drop it in favor of something that actually does. If RPGs have no distinctive features that distinguish them from games, lets just call them games.
As I said previously, I think that too much focus on the definition of "roleplaying games" overlooks reality. Every person has a slightly different understanding of what "roleplaying games" means, and their understandings almost invariably will be prototype-based. If you ask them if My Life with Master is an RPG, they'll blink and ask you if that's anything like D&D or maybe Rifts or Vampire, depending on their base RPG.
(Aside: One discussion at Wiktionary was over the definition of PC; ultimately the problem is you can't ask most people "do you consider an Alpha server running Windows NT a PC? What about Linux on x86? on Alpha or S/360?", because they have no idea what those mean, that those fuzzy edges exist.)
But in any case, not excluding story games from RPGs doesn't mean it has no meaning. Game creators have an understanding of what is and isn't an RPG; if a boardgame, no different from a dozen others, called itself an RPG, we could look at other boardgames like it, that neither the players nor the makers think are RPGs, and say it's not. But a lot of times it doesn't matter enough; if a storygame, daughter of Sorcerer, daughter of The Fantasy Trip, daughter of D&D, wants to call itself an RPG, I don't see the win in arguing that it's too similar to a theater game to be an RPG.
(Likewise, there are number of country bands that rock more then a number of rock bands, but as long as they don't cross the line too far, it's easier to let them self-identify then to try and define exactly where the line between country and rock is.
Or, are two people related? Siblings are, nigh-universally. Someone who is pureblood Kikuyu and someone who is pureblood Navaho (no close ties by marriage, either) aren't, even though they share an ancestor not more than 100,000 years ago. What about two random descendants of Genghis Khan? What about people who share a common great-grandparent? Does the fact there's no bright line, that one person might answer differently based on the context, really make "related" have no meaning?)
In any case, nobody is going to mistake bridge for an RPG. The fact that we can't draw bright lines doesn't mean the concept is void. When my friend says he likes board games better then RPGs because the choices are more limited and more concrete, I can understand what he's saying without arguing out the fine lines.
(continued...) Note also that lines are arbitrary and even mobile. In another universe where Dungeon was labeled an RPG and similar boardgames were also labeled RPGs, I'd be arguing that they're included as RPGs. Had the storygaming idea space been colonized from theater games written by people who didn't have an RPG background, I'd be arguing they weren't RPGs.