Blended-wing body makes a lot of sense for cargo/tanker aircraft. No issues with emergency evacuation procedure for passengers.
Has it been evaluated whether any real-life evacuations were time sensitive enough to where a wide bodied plane would have resulted in more deaths? Doesn't seem like a real problem intuitively, but I don't really have any data to back that up.
Aircraft fires can escalate extremely quickly, and in an enclosed space like an aircraft there's nowhere for smoke to go. Accidents also often result in less than optimal evacuation conditions. Fire may block exits, doors can jam, slides can fail to deploy, all of which slow down the evacuation. I've spent way too much time watching the Air Disasters show [0] and off the top of my head remember at least half a dozen or so accidents portrayed in the show where a plane was evacuated in minutes but some passengers were killed by fire or smoke because they couldn't get off in time. I'm not saying that wide body planes couldn't be evacuated quickly or safely (haven't really looked into them at all) but I don't think it's a situation where you can just say, wide bodies are more slow to evacuate and that's no big deal.