Steve is the PPT guru, so he'd know.
I also haven't heard of using PPT for Windows 8 Apps. As he says, presentations can be setup to do lots of complex functions if you are willing to "think outside of the box" and dig into the deep dark corners of programming PPT.
I do know you used to be able to buy addons that would "compile" PPTS into standalone EXE presentations. Could that be what you are thinking of? I have not seen recent mentions of them.
You could also create a PPT "app" and bundle it with the PowerPoint viewer.
A couple of techniques you may use in a "PowerPoint App" would be found in these tips about "Relational Presentations"
Creating a Custom Slideshow in MS PowerPoint 2010 -
http://www.itechtalk.com/thread9746.html
Create and present a custom show -http://office.microsoft.com/en-ca/powerpoint-help/create-and-present-a-custom-show-HA010338296.aspx 2010
Creating Custom (Slide) Showshttp://www.d.umn.edu/~hrallis/guides/PP/slideshow.html
Create a custom PowerPoint presentation from a set of slides -http://www.techrepublic.com/blog/msoffice/create-a-custom-powerpoint-presentation-from-a-set-of-slides/884
The Alternative to Traditional PowerPoint -http://www.indezine.com/articles/relationalpresentations.html
PowerPoint Rebellion: One Professor’s Pioneering Experimentation with Interactivity -http://www.indezine.com/articles/powerpointrebellion01.html
10 steps to adding a drop-down menu to a PowerPoint presentation -http://blogs.techrepublic.com.com/10things/?p=1505&tag=nl.e106
5 Minute into Video to Creating hyperlinks inside Slideshows -http://www.loyola.edu/edudept/facstaff/marcovitz/PowerPoint/HyperlinkPPT.mp4
Another place that this "PowerPoint Apps" idea may have come from is the newly renamed idea of addons being extended and called "Office Apps" I've seen a couple demonstrated and they can be quite impressive. I'm just not impressed with the name.