Yes, it’s a concern. But that doesn’t mean unfair advantages and cheating doesn’t occur in other esports.
Anyway, I don’t think we’re disagreeing on chess cheating. For me, the small chance someone is cheating doesn’t ruin the esport for me - For you it does, which is a perfectly reasonable response to it.
Secondary thought in the engine idea you had - chess fraud detection, I imagine, goes well beyond just the engine and move likeliness. It will also human-like interaction (Can’t confirm this, but the PM in me has me consumed with thinking about solutions to this problem)
When people play a chess game online, they are frequently evaluating positions. This results in cursor/mouse behavior that’s sporadic. If a user is considering moving the queen, they’ll move their cursor over to it. A user relying on an engine for every move would interact with the board in a very precise manner.
A player with a perfect engine to mimic humans will still get caught as their interaction with the board would differ greatly because only one position is considered for each move.