It's legacy info, actually, dating back to the 1.0 story quest "Fade to White." Up until now, most of us just assumed that 2.0's take on it was a retcon, as (2.0) Minfilia seemed to imply the Echo was the same for everyone, and was even doing stuff with hers she wasn't in 1.0. Perhaps the simplest explanation is that it starts differently for everyone, but always grows towards the same end result.