Ahh, that makes sense, and explains my confusion. So the air pressure will remain constant throughout the pad, which is fixed based on my total weight, whether I'm laying down or standing on one foot. But the fabric that is directly under my weight will be subject to the full weight of the part of my body above it, in terms of how hard it is being pushed onto the ground.
I will always use an 1/8" Evazote foam pad, so I'm not too concerned about punctures. I guess my real concern would be added pressure on the seams, where a pressure-related blowout is mot likely to occur.
I would imagine though, that being a Thermarest product, they must have a significant margin of error in the breaking point; whenever one rolls around or gets off the pad one is adding pressure points along the way. Assuming I am gentle when getting on or off the pad, I would assume I am within the margin of error when it comes to pressure.