It would be interesting to learn.
My concern is more directed at it drying or irritating the skin as opposed to it's catching fire. Before finding this site I had used it in the past with not very good results. I can't say it was the Barbasol or other canned goo I tried because in fact I was shaving wrong in the first place. Cartridge razors, bad prep and technique ect...
I suspect the isobutane is far worse than the propane in that aspect.