R. - Thank you so much for your hilarious post. I may have to save it for future laughs! I'm pretty sure your lil one won't spontaneously com bust in the middle of the nite.
I don't know this for certain, but here is my hunch about flame resistant pj's. God forbid one of our children got too close to a fireplace, a cooking range or maybe even a candle, those little pj's would be really tough to yank off to avoid serious burns if they ignited.
Now I can't imagine they'd go up like a bonfire immediately, but something must have happened too many times that somehow it's become a major safety concern. I'm more worried about the chemicals than the flame. They probably worry about it more at night because parents may have let there guard down, thought a baby was asleep and something awful happened - mostly you'd have fires and candles at night. Plus once they're mobile, baby daytime clothes usually aren't one piece.
I can say that about 40 years ago - my aunt was cooking in a zip up robe, the sleeve caught fire on the range and it went up in flames too fast for her to unzip and my uncle ripped it off her (that's the story they tell us!). So maybe at one point they made flame accelerating pj's!
have a great week end and holiday~K.