At their level of play, a single one-bit message can tip the scales in dramatic fashion. All you have to know is that there is a great move to be found in a particular position, without even knowing what the move is.
And it's a little bit of a meta game. Engines are ultimately playing against themselves when determining the best move. So they might discard a brilliant looking move because of some line that no human is reasonably going to come up with. Similarly they might make a brilliant move that humans don't recognize as such because no human can analyze as deeply as ane engine. So when a computer looks at a board and says there is/isn't a great move that's not necessarily the same as what a person would think.
1) To be useless to a top player, the decision tree needs to have only long term gains and be barren in terms of short term human-readable profits.
2) In the same vein, the metagaming pruning process you have described has to unfold a certain way, in the context of a game where most of the previous moves have been played by humans and not machines and where there is therefore much more of a chance of an unbalance compared to a purely computed position.
3) the above criteria of long-term, short-term, readability etc. must be defined according to players that are already 95% or so precise. The missing percentages mean that they always get smoked by machines over the course of a game, but can have a remarkable ability to see good lines.
You probably could rejigger the engine to factor into account the likelihood of a human finding the right moves and relative downside. Like an engine might reject a move that leaves them a half pawn down if the opponent makes 25 difficult to find moves in a row. But that risk/reward would be worth it going against a flawed human player.
Perhaps it could also work in conjunction with another GM that you train with regularly. They can use an engine and do the evaluation above themselves.
Sure, the human won't find the move every time, but it's still a huge edge.
https://lichess.org/broadcast/sinquefield-cup--grand-chess-t...
There's not a single move that significantly improved black's position.
From my experience watching tournaments, it happens regularly that missed opportunities would have given someone a 1 or 2 point engine rating advantage.
Funnily (to me) post-game analysis often highlights the computers finding incredible defensive resources instead of attacking ones. But it's exactly these kinds of moves - the fearless counter-thrust to equality while your king's position looks hopeless - that are the most inhuman of all and likely to draw suspicion.