I had heard about the horrendous burning deaths of ballerinas, an interesting article, but it says absolutely nothing about what stopped the flannelette from burning, a pretty pointless piece sets up the bait and then says nothing solid.
Interestingly, going down the rabbit-hole a bit found this letter snippet [0], which suggests this new fabric may have been less of a success in the long term than the article suggests.
This, cursorily looks to be a far better article:
https://montrealgazette.com/opinion/columnists/the-right-che...