Just because before android/ios there was no market for a personal computing device that wasn't either a desktop or a laptop doesn't mean a tablet is a pc.
Acer is confluing the two precisely because before touch interfaces, there was no "granny pc" to speak of. Now with a tablet, the "non-granny pc" is the one that's in trouble.
Putting the surface in the pc class is disturbing because it will not
1) run a lot desktop applications in an intuitive manner, because it's a user interface paradigm shift
2) will make any sense to classify tablets as anything but tablets once they overtake desktop pc sales
The two are seperate, and should be considered as such.
Microsoft HAS to make its own tablet, simply because the tablet makers don't make the OS, so what they are interested in is in making "addons" to an os, but the OS developer, when not making the hardware, basically has to pay the tablet makers to showcase the os features, which they are loathe to do, because it promotes the other tablet makers tablets... On the other hand, Apple makes the OS and the tablet, and doesn't sell the OS to others, so promoting the ipad is promoting iOS and promoting iOS for tablets is promoting the iPAD.