This isn't even remotely true unless you're playing at the highest levels of chess. I'm a fairly highly rated player on chess.com and I only know the first few

This isn't even remotely true unless you're playing at the highest levels of chess. I'm a fairly highly rated player on chess.com and I only know the first few moves of a handful of openings. I end up playing the book moves a lot but that's because I've played so many games and practiced so much that it's pretty intuitive at this point. I've never played 20 book moves, ever, in any of my 1000s of games.