An active individual can easily answer that question. Cotton sucks for many strenuous activities, period.

If you live in the north and are going hiking up a mountain through the snow, it can kill you. I leave in an hour to do just that. I will often put a cotton layer on in between synthetic layers, but that will usually come off as I get warm and it's always soaked. As long as you keep moving, you're fine. Get lost (and run out of calories or energy) or injured, and you can go into hypothermia in under an hour above 20f and significantly faster if there is wind or if it's any colder.

There has been some real improvement in wool products, and I'm switching over to products like Smartwool where I can.

To the "band aid" comments. No, it's not a silver bullet. Yes, we need to do better. Yes, it's better than doing nothing. Yes, this could be a step in the right direction.

Finally, it's early. Do we know if this process could become an at-home application? Then, you could reapply as needed and even retroactively apply to products that didn't include it initially.