1. I fully agree with Kostya: the responsibility lies entirely with the attacker. If you attack, it means you are confident in your superiority, have an advantage, and are ready to resolve the situation. The defender's task, accordingly, is to wiggle out of this situation—i.e., not to lose—and for that, as they say: all is fair in war (in chess, by the way, white initially plays for a win, while black plays for a draw, and stalemate is one of black's strategies for achieving their goal).
2. Why do you assume that such terrain is a bug, and that if the developers had known... Has it not occurred to you that the developers didn't just know, but specifically introduced such terrain as an element of randomness, perhaps to increase the significance of luck? Everyone here has somehow forgotten for a moment that this is SoD: with morale, GS, single stacks for the Miner, Pickendrams, etc. I consider terrain to be a continuation of this chain.
Specifically regarding this match—it's a complete joke. As they say in football: the pitch is the same for both teams. The loser even had a chance to use this "bug," but he blundered, as they say in chess, and was punished for it, which I believe is fair (Yes, I have also thrown already won matches due to stupidity or randomness. Does anyone remember me filing complaints?). In this match, it wasn't the terrain that decided it, but the winner's focus on the result, which proved higher than the loser's.
What is the spirit of the game? Who said that someone with even an obvious advantage must necessarily win? The forum is full of reports that do not support this thesis. For example, who can clearly explain to me: how does this terrain situation differ, for instance, from a situation where a folder with all artifacts is caught while speeding up, based on the spirit of the game?