Dyneema is a high strength fibre similar to DuPont's Kevlar. The fibre is used in rope, safety helmets, medical devices and anywhere else where tensile strength is needed. But at the end of the day its an ultra high length polyethylene chain - meaning that it will melt and burn like PET as would the elastane and the nylon in the jeans as well.

They will likely wear harder than normal denim but your weak points are likely to be other parts of the fibre mix, denim weave and stitching. If I was riding a motorcycle I would prefer to rely on a a specialist suit rather than these jeans because its as much about the engineering as the ingredients.