The idea is you need to make some suboptimal plays that you know aren't optimal, but where you expect to have an advantage over the opponent, either because you've trained on this weird type of line and they haven't, or because you're stronger than them to begin with and neither of you has trained on this weird line.

It actually is analogous to poker but not really poker as most people know it. It's analogous because poker is also done by training with engines; and you often want to make moves you know are suboptimal from your training because you believe it will exploit the opponent's suboptimal play.