You are correct in that it is valid for every tier one deck. The tiers have become less about how good the deck is and more about how many people are playing it. You could take any tier two deck and if it was played in similar numbers to that of any tier one deck you would see it do similarly in terms of number of top cut appearances.
In this case, correlation
may (don't get frisky on me here, guys) equals causation.
The number of a deck being played may be related to its tier. Considering a tier is subjective, the biggest quantification we have is the number of people running it in relation to its win ratio. People play a deck a lot because of one of two things:
- It is hyped a lot
- It is a good deck
Lostgar is probably the biggest counterargument to your claim. Even it did take quite a few wins, its ratio of plays versus actual first place wins was lower than the others. So in short, no, you can't any tier two deck, play it in similar numbers and then win with an equal ratio, because it would be outplayed by decks that are tier one.
The reason why a deck like Typhlosion / Reshiram is so widely played is not only because it has a strong matchup across the board, is highly resistant to locks, and can survive the current competitive litmus test (has an attacker that can return, survive, or mitigate the 120 Blue Flare / Bolt Strike requirement), but because it is cheap. Compared to previous format top tier decks, Reshiram variants can be acquired almost all through Trainer Kits and tin packs. It's main engine can be acquired through a Black Star Promo, and so can its main attacker. It's only booster-reliant (or single-reliant) card is Ninetales, and many competitive decks don't bother running it, so its a personal play choice.
So you've got sort of a mix-up in the logic there.