I'm probably sure it's wrong. The way the cards are created, you clearly see it has been designed from 3P or 4P to 7P. As you go for 3P to 7P, cards appear in doublons. If the game was designed from 7P to 3P, you would not see doublons (except the necessary doublons like resource cards).Alternate view-point. 7 Wonders is designed with 7 players (and no wheeling) in mind, wheeling is an unfortunate side effect of low player count games. Something you have to deal with, even though it's not part of the game as intended.
The wheeling has been exactly designed on purpose! It's a fantastic tool to get an automated balance of the cards. Since all cards travel to all players (minus the one you played), all cards can reach all players more effectively than if you had to draw from a deck. It also allows all cards to always be present at the same time.
On the business side, it's also much easier to sell a 3P/4P game than a 7P one. The force of 7 Wonders is that it extends up to 7 players, but I don't think it was intended for 7 players from the start.