Ambiguous slides are great because then you need to think about the problem a bit.Eh, sometimes you can clearly see the author just doesn't wants to spill his precious beans. When I see that I don't see it like "Oooh, learning opportunity!" I see it more as "Oh, what an asshole!". If you do research and you publish it, you explain it properly, otherwise don't publish at all since it becomes just a matter of showing off at that point.
Even showing off is better than nothing. Sometimes you just want to get some new ideas not how they should be implemented.
Just found this blog that talks about more on this.
http://c0de517e.blogspot.fi/2015/04/sharing-is-caring.html
He's referring to many of research papers, often coming from universities, that do this (present a new technique with no code or means to reproduce the results) making it useless for any practical purpose.
CryTek's slides are a bit different because they're just explaining 'this is what we did'. It is already proven to work (it's in their games) and obviously they won't give you everything in silver plate to reap off their efforts w/ copy pasting. They give enough to figure the technique on your own.
Of course the more they share, the better.