My opinion was based on the info id heard about nibali improving his position and now clearly improving his tting....
Also people always talk about wiggins perfect position being flat
Nibali may well have improved his position that does not necessarily mean getting lower and flatter though, there are many variables to a riders position, and even more variables governing how fast a rider will go.
Wiggins position is always talked up as the perfect position by commentators, it way well be a great position, but it is a position that is great for him (Matt Bottrill has a similar position).
As I said, if interested, look up some of the top UK testers (many of which seem to use the same wind tunnel service, drag2zero) and you will realise that they all come out with different positions that are optimum for them, on the bike they ride. Some will be low, long and flat, others like an aero cannonball!
The reason I recommend looking at the top UK testers is that they are not governed by the UCI in most competition, so many will not remain UCI legal throughout the season, they will take the most aero and powerful position they can, within the much more relaxed regulations of the CTT, so you get to see what variance of optimal positions there really is without having things limited by lots of regulations. To add to this, many of the top guys would be competitive in a pro time trial.