I suppose that the recipe information made it into the journal, but the actual trap didn't.
I thought this kind of trap would be the most overpowered so tried assembling it ASAP, but to no avail. Then tried the smoke grenade variation just to check out the new building system which is really awesome, but there's unfortunately no visual feedback on whether the building will succeed or not. Don't suppose ArmA will allow client-side checking though, but I'm no modder to be sure of that.
Anyway, I thought the wire traps would work nice when booby-trapping building entrances - a long farmhouse, in my test-case. But the system disallowed to put the trap just inside the entrance or outside. You generally can install the trap some 1+ meter outside of an entrance, but the wooden columns become too apparent and easily detectable. Maybe it's better for everyone, as putting traps inside the major chokepoints and bottlenecks is certain manslaughter, but damn I was sure it would be fun :)