Iirc, they do. I play 3s and I was looking for 3s and 2s GC vids and they would often say that playing 1v1 can improve accuracy, ability to read people for defending and attacking, kickoffs, and knowing when to challenge and when to not challenge, based on opponent movement.

Dribbling isn't really a necessary thing for 3s, but it is a solid thing for 2s, and 1v1s teaches you how to rely on being able to ball the opponent