Tarrasch also followed this idea. The problem is that every game begins with opening, but not every game reaches the endgame.
Learning by heart is not the only way to learn openings. Somebody could lay correspondence chess and use a book to go through the opening. Or train in Chessable and limit the opening to 4 or 5 moves, which reduces a lot the study time.
But yes, Chernev’s or Euwe’s books are an excellent option to somebody to get an orientation in how to play the opening, with the advantage that all phases of the game are included. I began to learn with Euwe’s books.
Black
Or
White
Nothing in between
Opening is one aspect of the game
Not the most important but also important
I agree with this and you're right,this is why "amateurs" are told not to learn Openings. However don't you feel that amateurs would benefit more from learning Tactics and Endgames with just limited Opening studying or just knowing the principles of Openings,that should be good enough.
I personally believe that any raw beginner should buy a move to move book like Irving Chernev's classic "Logical Chess move by move" and try and go over a few of those games just to understand the overall flow of the game,the way it should be played,general mistakes to avoid and so on. I also personally believe that most teachers/experts etc. put maybe a bit too much of an emphasis on tactics,thus neglecting other parts of the game that are very important. Even still though,I'd go with Tactics and Endgames,it's like Jose Raul Capablanca said, " In order to improve your game, you must study the endgame before everything else. For whereas the endings can be studied and mastered by themselves, the middle game and opening must be studied in relation to the end game.".
Therefore it would make sense to study the endings,Chess is best understood backwards to forwards,strange as it may seem.