Well-made seams and seam-sealer are enough to take care of leaks. OP notices than too many makers would seem to limit design to fabric width and labor cost considerations. Methinks Gargoyle Gear are three-panel tarps.
The center seam at the ridge-line offers the advantage of being coincident with the line of tension. It doesn't stretch much as the fabric is folded and stitched comprising four layers, and doesn't create unpredictable luffs in the tarp as the three panel design might. Shape can be modified as the designer likes to create a saddle, if desired.
Here's Warbonnet Outdoors explanation:
All our tarps are made with slightly caternary-cut ridge seam to achieve a tighter pitch. They have lightweight low-stretch polyester edge binding on the ridge seam. The binding along the ridge seam makes for an extra-strong low-stretch ridgeline seam that eliminates the need for a separate ridge cord, it also means you'll never need to seam seal the ridge seam.
Nothing stops you from including the same features even within a single width of fabric.
There was a tarp maker who used different fabrics for the parts of three-panel tarps,