When people buy something they are paying and buying now, they are not buying someday or wishful thinking unless disclosed to them not available but upcoming features.
The export is not Construct, but some other software, I think it should be clarified that Construct does not natively export directly to the advertised platforms and requires a 3rd party to do it.
But scirra never did say it exported natively to iOS, Android, Windows Phone, Windows 8 or even Desktop. In fact, they didn't even say it was easy, regardless of whether it is native or not.
While it's a bit of wishful thinking to emphasize Desktop and Android equally, since it works orders of magnitude better on Desktop than Android/iOS/Winphone/win8, there are some games published on those platforms, to it's not "false advertising" by any stretch of the imagination.
It's harder to target mobile, and mobile versions of games are always less capable than desktop versions (unless you plan for mobile first), but isn't this universal? I know for a fact that GM or MMF games for mobile aren't as capable or performant as their desktop counterparts.
TL;DR; Yes, it's a stretch. But then again, all competitors make the same stretched claims. Also it's not false advertising because it is indeed viable to publish on those platforms.