they do not want neither to concede this duel (it lowers Rank) nor to win it (it raises Rank) - they want the match to end fast with a Draw.
You might not know this, but a DRAW in Magic Duels is treated as a loss.
During July-August 2015 there was an older chinese trainer for Duels, it wasn't nearly as polished as Antifun's work, but it had a similar option to insta-win games by lowering opponent's HP to zero.
It had an issue tho, if "zero hp" cheat was active before going into the match, both you and the opponent would end up with zero health.
Hence, a Draw screen appeared. I had it myself many times.
Magic Duels treats the Draw as a loss for both players. Rank is lost and no gold is given.
Therefore, the draw you are looking for, would just end up in a loss of Rank.
Besides that I simply find silly to be worried about loss of Rank, when you are clearly talking about a cheating trainer that allows insta-win in multiplayer matches.