The 3 inconsistencies in chess.
1. If u can capture your opponents pieces, u should be able to capture your own pieces
2. If u can promote to your own color, u should be bale to promote to your opponent's color
3. If u can promote to a knight, bishop, rook, or queen, u can definitely leave the pawn as a pawn and promote it at any time u wish.


Reading the article posted on page 1 or 2 that this idea originally came from (too lazy to find it) basically someone came up with a contrived example for a cheeky puzzle based on a poorly worded rule that FIDE had. So, when the rules of chess were codified by FIDE someone took for granted that nobody would be stupid enough to actually think this was a thing (and if you tried it in a tournament it's unknown if the TD would have even allowed it). Then some smart aleck guy notices a potential for the rule to be used in an unintended fashion, makes up a stupid puzzle and is smug about it (or maybe did it just as a joke), then FIDE says that's stupid and changes the rule to explicitly state back rank which everyone already knew was the rule anyway.
This sometimes happens in sports, sometimes in law, and pretty much always is adjusted immediately to prevent potential exploitation. People are not infallible beings, especially when it comes to codifying complicated ideas.
TLDR; It was never a rule and never intended to be a rule. Someone purposefully misconstrued a rule that wasn't written explicitly enough to be cute and it was changed, likely never once having been used in a real game.