Agreed. The longest game of Kill Team I ever had was about 1.5 hours and that was due to teaching a new player how to play, neither team really killing anybody (Scouts vs. Necrons) and new player taking their time to really learn the rules. That game also ended in a draw after 6 rounds with neither side gaining an advantage. I can't really imagine a game of Kill Team taking much longer except if were two newish players both with teams of 18-20 models. I have had games as short as 15 minutes in Kill Team with both sides being elite, sparse terrain and very lethal early rolls. I always had the impression that Necromunda would be slightly more involved and thus a little longer of a game. I think that is what is skewing the poll results longer than an hour. I can't tell though, since poll combines both games.
If separate Kill Team poll is created, I would suggest collecting votes for: 30 min, 45 min, 60 min, 75 min, 90 min, 105 min and 120 min. You could ad a greater than 2 hours vote too, I just can't see that being the average game length by players not taking several long breaks while playing.