Right, I think you hit some of the notes I've been hitting. Is it realistic for a group of creatures to employ deathtraps within their own lair? Maybe, maybe not, only the GM can decide, and who's to say why they chose answer X? Are the little baby bugbears so well-behaved that none of them is endangered by a deathtrap? For how long can that be said to hold? How exactly long can a group of ambushers remain in hiding at full ready for someone to come by? An hour? A day? What is the probability that the PCs do or do not happen to be passing at a moment of readiness, or unreadiness? Is the guy in charge smart enough to send a scout down the path? Do the monsters have a means of signalling, and what is it?
All of these things are easy enough to make up, but I've only scratched the surface, and the real point is, the GM IS making them up. There isn't any reality which dictates the answers, at best there might be a genre convention or something (bugbears are sneaky and patient, the MM says so, but they are also stupid and primitive). The point being 'WAR' or 'SPORT' is just about what the GM made up, and maybe how the players reacted to that or what they asked for.