There are not many PCs that are THINNER than the current Air. The current Air is pretty damn thin. So much so that it has to use a Y-series Intel chip, which sucks for performance. So, your point about there being thinner laptops, if even true, is moot because the user experience is still crap.
I was talking about weight all along, mentioning the thinning effort which led to the butterflygate only as an illustration that they do care about having the most portable machines.