A recent game of mine opened with the moves 1. d4 d5 2. Nf3 c5 3. c4 dxc4 4. e3 cxd4 5. Bxc4 and now my opponent played 5…Bg4 allowing a variety of strong moves including 6.Qb3 and 6. Bxf7+. After the game he said something about ‘not knowing the opening’ and left.
I didn’t say anything but felt that the problems with 5…Bg4 were not knowledge related. It was clear to me that Black’s pieces are in a vulnerable situation after 5…Bg4 and the tactics would need to be checked.
This is actually true of the opening in general, a large part of good opening play is down to general skill rather than knowledge. The obvious application is in an enhanced ability to improvise, though there’s even more to it than this. More skillful players will be better able to remember opening ideas and themes simply because their superior perception allows them to hang the moves they see on hooks of understanding.
This is one of the major reasons stronger players have greater opening knowledge. It’s not down to having more time available for study, it’s that they’ll learn them a lot faster.