I tested the same procedure in FG classic and it worked as well. I gave the Dragon NPC a custom special Ability with [Wounds Threshold +3], and it was incapacitated after receiving 8 wounds. (3 from WC, 2 from size and 3 from Wounds Threshold). I didnīt use resilent or very resilent to add wounds at all.

Very important is the right spelling of the code. When I first tested it, I wrote [Wound Threshold +3] and it didnīt work because of writing wound instead of wounds.