This is a more complicated one, because certainly there can be threats to play that shift the score by huge margins. But I think if the server is looking at the game score, the availability of huge threats does not impact what it thinks the likely end score of the game is because there are simple answers to those moves. If you and I are playing, and you are 99% to win, and I make “ko threat” kind of move that threatens a huge group, the server does not switch to me being 99% to win until it sees if you’re going to respond to it. The server knows that you are going to respond appropriately and the game will not change.
So I think that the “server thinks no move changes the score more than .49 points” rule works fine.