There are many chemicals used in the products we wear that cause all kinds of nasty diseases, but the hub bub around PFAS is exactly because they are "forever chemicals." Most lab-made substances break down over time, but PFAS are particularly horrible because they never break down. PFAS are generally used in waterproofing everything from jackets to shoes and bags, but they contribute to a variety of human health problems including cancer and birth defects.
I applaud Keen here for figuring out how to create the same end result, water repellency, without the crazy chemicals, and then offering to share this intel with the rest of their competitors. It goes to show that the other folks who claim that they don't know of alternatives or need many more years to figure it out, just aren't trying hard enough. Keen has even created a webpage and “Green Paper” outlining exactly how others can follow in their footsteps.