(On mobile so will try to respond to the main points but might not hit every individual point.)
Fair point that I was thinking specifically of the threads, not the published articles that include the write ups where you could easily see a Pokémon’s optimal catch method as you’re looking up its ranking. With that being said the threads do take a long time to complete in some cases - I mean, GSC’s rankings were just updated this week and are still being actively debated. People have had to rely on that thread for literally years since there’s no article for it yet (at least not that’s linked in the IG tiers link master post) so I think it’s reasonable that the threads should be treated as a resource as they’re being developed and not just a quick working document until the final product is published.
As others have pointed out in most cases “catch ASAP” is the best method, so arguably there’s no point in doing this for a handful of fringe cases. On the flip side of that, though, you could argue that since there aren’t that many where it makes a difference, it wouldn’t require that much effort to update the lists and/or write ups for the handful of Pokémon where it is applicable. And as noted above there is precedent for this in the RBY write ups.
The original example of Spearow vs Spearow (Kenya) is moot since wild Spearow was just moved to S in GSC anyway, but there are other examples where it matters (all of these are taken from discussions in the GSC thread): Abra, as I mentioned before; Teddiursa, who is a huge pain if you attempt to catch it as Teddi (low appearance rate, low catch rate, high run rate, limited availability hours) but is much easier to catch as Ursaring and also doesn’t require babying if caught pre-evolved; and the aforementioned Psyduck, who’s excellent if caught at a point when you have access Surf and Ice Punch to teach it but can be pretty much dead weight before that.
I’m completely ambivalent on changing the tier lists in the threads, and if people think it will be too much work or will make the lists too convoluted then that’s fine. But I definitely think it should be noted in the write ups where applicable.
Edit: one additional thought, if the assumption is “Pokémon are tiered once based on optimal form,” why are trade evolutions ranked separately? We already have that precedent for ranking Pokémon twice depending on a particular condition, and those don’t even always affect viability (eg Golem and Graveler are both A in GSC but Geodude is ranked twice). If the standard is “don’t rank twice unless they play dramatically differently” then trade evolutions in the same rank should probably be combined.