I don't know which of these techniques they actually built, my experience with these techniques is several encounters with salespeople from multiple vendors who present them running on FPGAs and then compare performance to non-approximated versions of the same network on a GPU to show the amazing speed gains with minimal reduction in test set metrics. This is, of course, not the whole story.

My response to them is to tell them to implement and compare against the same tricks on a GPU if you expect me to believe the throughput performance delta. I usually get some hand-waving about how that's not possible or pointless yadda yadda yadda and the conversation goes downhill from there. That doesn't mean I don't like these tricks or that I don't think they're useful, it means that based on the scars from a very long industry career I don't buy snake oil.