The record in question is the shortest game to end this way. Now this game isn't the shortest, but it is one of the shortest. The shortest game to end with KvK was only 17 moves, but this was clearly a collaboration between the two players ( Haimovich and Zifroni). The next shortest game (in my database) is 35 moves, one of 10 that finish before move 40. However the players in these games were either unrated or lower rated, but of course a game is still a game.
Therefore the Svidler Nepo game might not be the shortest KvK game, but it is certainly the shortest GM game to end this way. The nearest rival looks to be a 43 move game, and unless there is some implicit collusion in the future, this may be a record that stands for quite a while.
Svidler,Peter (2762) - Nepomniachtchi,Ian (2703) [E60]
TCh-RUS Men 2016 Sochi RUS (1.1), 01.05.2016