The warning on fabric mostly has to do with burning, and what toxins are given off when the fabric is ignited. Parents think there is such thing as flame retardent treated fabrics. And will only buy treated ngihtwear. I can't but stress that you must make your own decision on what type of material you want to use.
The warnings were put there because people assumed that fannel was flame retardent. It has never been. People sued the manufactures and now they must put those warnings for anyone who didn't know that cotton burns.
There must be classes somewhere where people can learn how the fabric they use reacts to flames, and what toxins are released during burning. Of course I learned years ago [1950's-1970's] in sewing and chemistry classes. Back then the schools thought females who would of course be homemakers needed to think of family safty.
Check out the internet and see if they have the information on fabric and fire. If you can get instruction on building a bomb you should be able to get some information.
note. when those plastic dolls people give their children, and stuffed animals they allow children to sleep with catch fire not only will they melt all over the place but they give off deadly fumes. See any warning on them? I don't know I don't give them as gifts.