Are the pertex weights listed "finished"? Doubtful, they rarely are in marketing literature. Intrepid and M90 have finished weights around 1.05, but it varies by batch and color by a bit. Lightest I've seen was the gray that came in around 1.00 as I recall. All fabrics have some variance by run. The new SevenD fabric is actually 0.65 finished weight.
My experience with Pertex Quantum has only been in finished products, but personally, from what I've seen of it's downproofness and dwr have been less than impressive. From my experience, Intrepid and Momentum blow that stuff out of the water.
Honestly, the SevenD and M50 (I haven't tried M55) still seem superior, with M50's downproofness being around the same as pertex, i.e. a bit leaky, but totally functional.
Pertex is just one of those names, it's been hyped up and proliferated so heavily due to it's industry adoption, you can't help but think it's the best fabric out there. In reality, it's likely just the best "resource" for a large company that was looking for some really light, off the warehouse shelf fabric a few years ago, that it didn't have to get custom milled. YMMV, but I wouldn't waste my time with so many other options available to the MYOG community now.