Yeah adding corner geometry obviously isn’t the way to go here 
There used to be this one particular tech talk on YT that at least showed what this slide was all about.The guy indeed demonstrated the unchanged wireframe of the rather crappy mesh and with PADM it was like an instant-awe transformation. I’ve since then used CryEngine very little and stopped altogether the moment UE4 went out of beta so my personal experiments with PADM are kinda limited. I did manage to produce a rocky displaced plane with nice looks no problem but as to the under the hood how, no idea whatsoever!
Is this the same stuff? http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter08.html
Not quite right?
The one thing I do recall is there were no visible silhouette fins in the wireframe so they probably used something at least slightly different.