Skip ahead to about 11:10.
I remember way back Burnham telling me how easy it is to cut a cable core with a small saw. We finally tried it at a training a few years back and it was super easy (I'll have to find that video) We had more tension on the lanyard though. I think buckin's only lasted that long because it had minimal tension on it and could move around a bit.
I do remember thinking that a glance from a limbcut follow through would be unlikely to cut all the way through. It seemed to take a little more effort than just a glance, but probably under 2 seconds though. And with a big saw, I'd imagine a glance would do it pretty quick.
On a side note, we found bolt cutters don't work all that great to cut through a cable core. We broke two cheap pairs and had to really gnaw with a good pair to get through one. Found that the skinny steal part of the snap hook cuts easier than the cable if you're using bolt cutters.