I don't know if I always agree to study the endgame first, but it should be studied very soon after learning a few basic opening principles.
One reason is because it would suck to get into a winning position and then throw it away because you didn't know a simple end-game strategy.
One of the most embarrassing situations is to have a clearly winning position, then get swindled into a stalemate (which is a draw even if it's your opponent in a stalemated position).
New chess players should quickly learn how to get a checkmate from KR vs K, and they should also know that a king and two knights can't force a checkmate (you can only win this if your opponent blunders).
I don't know who said that beginners should first learn endgames and then work backwards( perhaps capablanca said it). But, he was totally wrong. I think beginners should not waste their time learning endgames(except perhaps the most basic like k vs R+R or K vs Q+R. I think players below 1400 should not delve into endgames because those players would be far better served learning openings or practising tactics. The endgames rarely decide the outcome in <1400 games. Even if some games are lost due to poor endgame technique. Its better than losing lot of games in opening or middle game. Some are saying that endings are easy to learn because there are few pieces. But that's again a wrong view because as the pieces become lesser, chess becomes a game of squares and tempos. These things are obviously harder for beginners to understand than basic middle game combinations. Endgames start becoming from 1400 onwards. Until then, players should forget about endgame theory. They should focus on simple ideas in endgames, like checkmate(using queen and rook) and stopping the opponent king from getting into the game by building a firewall using queen or rook.
A player anywhere near 1400 is not a beginner. Even a player rated 1000 is not a beginner. A beginner would be ranked about 600 to 800.
The first thing a beginner should learn is the endgame of how to mate with K and Q vs a lone K.
Then how to mate with a K and R vs a lone K.
Then maybe how to win an endgame with maybe 3 pawns vs 1 pawn.
Then maybe how to win other simple pawn endgames.
Then maybe how to force a trade to get to one of the above endgames.
After learning the very basic endgames--that is the time to go into other subjects.