Getting any kind of information from a chess engine would be sufficient to gain an edge for a good player. Even something as simple as a nudge that there is a high value move in a position with no information about what the actual move is could be enough. Big chess tournaments tightly control phones and other devices for this reason. That's on a single-match level. On a tournament level there have been allegations of collusion where players will intentionally arrange their own matches to either be quick draws (to get a break to focus on other matches) or to give points to a designated player to help them win the tourney, Fischer famously accused Soviet chess players of doing this.