I was up there around 6 weeks ago when the fence was getting built. I was only on the 2 munros but a slightly different route from the WH one. Coming off Beinn Teallach there was a gap in the new fence.
I spoke to one of the guys building the deer fence, which at that time was going right up the side of Beinn a Chaorainn but probably hadn't quite reached where you have marked it on the map. I asked him where the fence was going and he said it was going straight over the hill. He said it was a conservation thing similar to what has been done at Creag Meagaidh with a natural woodland and reckoned there would be gates going in if it was a popular route. Maybe you missed them or maybe they didn't go in.
I noticed a lot of the forestry stuff from last time I was there was felled but possibly unrelated.
I didn't get the vibe that they were trying to stop walkers - which is going to be impossible on munros anyway.