Yes you are right about the Uruk-Hai in LOTR, I think they were copying this thing down there in New Zealand. They also had pikes (sort of) and functional armor and gunpowder weapons. I think I saw Sallet helmets too. In a way the Uruk Hai were the closest thing to late medieval army in that movie. The Gondor dudes didn’t even use lances in their charge and their armor was apparently made of cardboard.
I think these latchet crossbows were an historic development. Anyway at least three functional replicas were made based just on the Löffelholz manual so I think it’s clearly a viable design.
It is a light weapon as medieval crossbows go, Bichler mentions his has about 100 kg draw weight. I suspect the handle would hold up if you made it with the right materials.
It would have limited value as a weapon, not really ideal as a military weapon though it would have some utility for a horsemen (such as as a backup weapon). I see it as a personal defense / hunting weapon ideal for horseback. Maybe equivalent to carrying a small caliber automatic pistol like a 9mm for personal protection. Not something you would use as your main weapon if you were in the military and being deployed overseas, but it might be good as a backup.