What about this even RARER idea, then? (Opening; Vienna Game)

1.e4 e5 2.Nc3 Nf6 (or Nc6 or Bc5) 3.Rb1

Has NEVER been played OTB (!);
According to the engine, it makes *less* sense vs. the Falkbeer Variation (any idea(s) why?) – but it's okayish vs. the Max Lange Defence and the Anderssen Defence;
Very rare even in the Lichess Database!
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Related to: lichess.org/forum/general-chess-discussion/is-this-rare-idea-good-opening-four-knights-game

Not sure why you seem to find Rb1 so fascinating.

@Neverness
Previous one was not rare rather quite normal on online chess.
Don't know why you find rare openings!
It doesn't matter since they aren't bad alternatives either. And there are many different online chess sites not only Lichess.
Almost half of possible chess openings have never been played so would you list them all?
And every opening transposes to some common middlegame position so there's no special in different move order.
Hence, it's neither rare nor special!

What's your obsession with obscure side lines of openings. At least Gotham Chess fans are having a field day with all your rb1 lines.