Normally I'm the more conservative of the two when it comes to map/server changes, with Elfbarf pushing for change if it's a genuine improvement, so if he's against a map version update then it's probably for good reason.
For my own take, I'd say the overtrapping of the pathway to the traitor tester is going to end up being a net negative when it comes to gameplay. Downstairs can undoubtedly be a hotspot in v3, that much I won't deny, but it's never really been overbearing to the point that player traffic heavily concentrates there every round. The drowning trap is already enough of a death sentence that innocents are more than hesitant enough to go through it, which in my opinion is a good thing since it prevents the traitor tester from being too busted.
As for that area being so overtrapped that it pushes people towards the cars, I don't think that's as much of a positive as you make it sound. If an area is so overtrapped that innocents just avoid it entirely, then that's reducing options, not creating them. The cars are a great peripheral to the map, but trying to shift it to the map's focal point will only highlight that area's flaws that are otherwise benign. The car area is big, open, and you can see pretty much everything going on barring a sneaky knife kill around a corner or someone scouting.
For me the secret knife is just the nail in the coffin. These things don't work unless they are done extremely well like in ttt_mc_christmastown. There it's a whole song and dance where you have to search for materials and is almost always a group effort, so people are more aware of it being completed. Not only that but the traitor item you get is random so it's not always a knife; but even if it is and things devolve into chaos as a result, by that point the objective has taken so long that it's near the end of the round regardless. We've actually had to skip over some potentially good maps that were ruined by "secret" knife spawns, where someone immediately grabs it and things devolve into a shitshow, so I'm even more sceptical that this updated version will be better than the original, which has always been a big fan favourite on the server.