These comparisons are a bit silly. Simply enabling the settings Ubisoft left disabled does not have a massive impact on the visuals. And most importantly it does not unlock the e3 2012 version...explosions are still not like they were in the initial trailer.
The second video seems to be heavily modded (or should i say edited), with a much darker, richer colour scheme. That can have a huge impact on the look of the game similar to what was done with Skyrim.
That was obviously a design decision. When he does a blackout in the second vid you cant see shit. Yeah it looks great but i mean really?
The first video is also not a like for like comparison...so not sure what they are trying to achieve with that video.
Yes Ubi was wrong to do what they did, but considering the minimal impact it has on visuals i would say people are overreacting.