The lacquer seems to do the trick. Having said that, I am more about tying to induce a strike than for durability.
One of my hero fly tiers was Fran Betters. I watched a video of him tying one of his Ausable patterns. When he finished the fly, he said: "There, that fly should be good for catching 50 fish" - paraphrasing him.
Since I tie my own, and enjoy doing so, losing a fly to a trout's teeth doesn't bother me at all. I would rather that happen than to have tied a "bullet proof" fly and not enticed the strike. After all, the insects we are imitating are quite delicate themselves……..
Just my way of looking at it.
The dubbing on the thorax in both flies is SLF - Whitlock's mix.