There are many different ways to frame the conversation, and I think the question is who is arguing what, and is it suspiciously a convenient metric for someone from that fanbase to argue from.
For instance, in order, 49ers fans would LOVE if the right way to do this were:
1A) Success of the franchise, as measured by Super Bowl wins, over time.
1B) Success of the team, as measured by division wins and playoff wins, since the two new regimes came into place two years ago.
1C) Success of the team, as measured by the records against each other in the regular season, since to the two new regimes came into place two years ago.
In turn, in order, Seahawks fans would LOVE if the right way to do this were:
2A) Success of the team, as measured by total point differential against each other in the regular season, since the the two new regimes came into place two years ago.
2B) Success of the team, as measured by division wins and playoff wins, since realignment when the Hawks have been in the NFCW.
2C) Success of the team, as measured by this current season so far.
NONE of these six things are OBJECTIVELY the correct metric to use. Instead, we see each fanbase opportunistically employ the metrics that are most convenient to arguing for their team's "obvious" superiority, and mostly in order too in order to make their case appear to be more airtight.
On 9ers boards it is "obvious" that 1A-1C matter and that Hawks fans are homer idiots who have deluded themselves into believing that 2A-2C matter. In turn, on Hawks boards (and for example, this thread) it is "obvious" that 2A-2C matter and that 9ers fans are homer idiots who have deluded themselves into believing that 1A-1C matter.
We can get in all the little scrapes about if "history" matters or not (for Hawks fans history doesn't matter if we're talking about 1A but does matter if we're talking about 2B and for 9ers fans history doesn't matter if we're talking about 2B but does when talking about 1A), but IMO it's basically just obscuring what's happening:
Yes, if we are assuming a world of logic and reason than privileging 1A over 2B or vice-versa while ignoring or minimizing the other is a clear contradiction of logic.
Instead, if we are assuming a world of opportunism and homerism than when talking about "history" privileging 1A over 2B or vice-versa while ignoring or minimizing the other is totally normal and to be expected.
Basically, if someone is trying to convince you that fandom exists in a world of logic and reason, they're trying to sell you something. We know this because really nobody's fandom origin story comes from a place of logic or reason: it's mostly born out of where you happened to grow up, and if not that stuff like having a relative who happened to be a fan of a team, or having a long-since retired favorite player be on a team when you were a kid, or that team being on TV a lot when you were a kid, or just randomly picking one when you started watching, or liking a uniform that has probably changed since then, etc. etc. Instead, fandom exists in an emotional world that's rife with opportunism and homerism, and according to that logic, this whole conondrum makes perfect sense.
Long story short, if someone immplies there's "truth" to their position beyond just opportunistic orientation and the homerism that comes with fandom, they're full of sh!t. It's not that people "don't get it", it's just that they choose different things to "get" based on what makes them feel good about their fandom and their team. It's why you NEVER see a 9ers fan giving any credibility to 2A-2C and NEVER see a Hawks fan giving any credibility to 1A-1C. It's all just a bunch of bullsh!tters opportunistically bullsh!ting.
I will say also that a somewhat natural extension of this is moving beyond the fandom of one's team to the disparagement of an opposing team, and then again beyond that into the disparagement of opposing fans as all inferior, immoral, stupid or what have you. That's a degree of tribalism that goes too far IMO. While it would be nice if fans didn't act like opportunistic homers in deciding what "counts" and "doesn't count", we'd be asking too much because doing so basically contradicts the logic of fandom. Instead, we should ask that the tribalsim not extend into petty attacks on other fans, which is just unnecessary, going too far, and frankly pretty pathetic IMO.*
*Spacing this from the rest of the post because it is an addendum (meaning, it shouldn't get in the way of the above which is think is "true" versus what follows which is an opinion) and I know it will be an unpopular one here: : As a 9er fan -- and I've said this here before -- personally this really only gets my goat when some Hawks fans talk about 9ers fans as being "thugs" and "criminals" and the stadium being not safe, etc. etc. (e.g. 9ers fans are criminals because someone in a rap video about the 9ers was wearing a bandana; the shock!!! the horror!!!). Even when not intentional or conscious (which I think is most of the time) I sadly know what these code words mean, and it annoys the ever loving hell out of me. That's the type of "too far" that I'm talking about.