6 and 10-ply tires don't actually have 6 or 10 plies.
That's a bit of a misconception and the ply rating system goes back to when all tires that were made, were bias ply.
Nowadays with radial construction, the higher the ply rating generally means the heavier the cords are within the construction, and also how densely the cords are spaced.
Basically, the higher the load rating, the more actual material there and the thicker that material is, but it does NOT have more layers of material.
That's why I say you'll likely have "some" additional protection from punctures, and added longevity. That's also the reason the E tire is stiffer than a C tire.
That's tire tech for today, gotta go back to work now.