How do dry verges work/how are they watertight

[Michaelsf90]

Weve recently had our porch flat roof removed and a pitched roof put on by a family friend who's a roofer. Hes put dry verge on but I'm wondering how is it watertight? I tried to straighten it up as it looked twisted and wonky as you can see in the pics. But I noticed there is nothing at the side of it so how does it work. How is it water tight when it isnt sealed?

 

[Vinty]

 

[^woody^]

It works via the overlap.

Whether your roofer friend has finished the membrane correctly is hard to see. But he's certainly used incorrect hollow soffit as vertical cladding