Took me a while to sit here and look at the cut, to the lace, to the cut. I don’t think it will leak. I have to say, 30yrs of roofing, I’ve never seen a valley cut, then laced in the middle, then cut up the rest. I’m not saying it’s wrong. Anyone who would have done this, has done it more than once, so it must work. I would make sure the shingles around the vent are sealed to the vent with some good roofing sealant. I never lace laminate shingles, because ARMA doesn’t approve it. Course, lots of things I do, work. They just might look weird.
I do a closed cut valley different than this one with a laminate. I’m good with it.