Ok this will be my last word on Pidgey, since I don't want to drag this out any further, but I wanted to explain some of my philosophy behind how I decide tiers.
Firstly, I'm of the opinion that early availability doesn't mean anything unless the pokemon is worth something in the long run. This is the case in pretty much every pokemon game. For example, in DP both Starly and Bidoof are high tier because not only are they available early, they contribute something meaningful to your team that aids efficiency greatly. Starly has a great movepool and stats, making it a great battler that also doubles as a Fly slave (and Defog I guess but you don't need that). Bidoof is a poor battler but it evolves into one of the best HM slaves in the game. Compare that to something like BW Patrat, who is available very early but is mostly worthless in the end, making it Low tier. Liekwise, RBY Pidgey, for reasons I've already given, just isn't a worthwhile choice in the long run if you are playing for efficiency, hence making it Low in my eyes.
Secondly, I think we can all agree that this game is incredibly easy. It is very possible to simply pick 1 pokemon and solo the entire game with it. In the end, pretty much everything in the game can be ay least 'decent' if you willing to train them, with the possible exception of Ditto. Therefore, I think that when we decide tiers then we need to make our standards a bit higher than we might if we are playing a different game. If we are willing to put things like Pidgey into Mid, then you might as well just have Ditto in Low and everything else at least Mid, which would make our list look simply stupid.
So yeah, those 2 things might give an insight into why I went with Low for Pidgey in the first place. In the end it's Mekkah's call though.