With Lab Builder, there is a very high chance that he never activates Jurrac Impact, since the last turn, the very first card you usually activate is Sword and Shield, and with that, no monster of his has 2500ATK any longer, therefore you may not even need arrows, tools or anything else...
So far, he won't activate it on UG unless you start buffing things up big nenough, so I just pop a Forced Ceasefire first thing on last turn and that's it. I think AI would not see UG as a risk big enough to wipe the board along with its own 3.8k beater.
He won´t activate it even with Master of Oz in the field, it looks like he´ll just activate it if you attack a dino, if you use secret pass and attack him directly, he won´t activate it, at least, that´s my experiencie