As an American, I've heard that this can happen but have never heard of a specific example of it happening accidentally (sadly, there are multiple examples of them being deliberately used as weapons). I suspect it's an old wives' tale, possibly an exaggeration of poorly-made or damaged cookers somehow being opened at pressure and the "explosion" actually being rapidly venting steam.
I once tried to pressure cook a large pot of habanero peppers (to make hot sauce).
(While doing this I was drinking with friends... bad idea)
I wanted to open the pot and so put it in the sink and ran a little cold water on it until I could just get it open. The resulting steam hit me in the face and hands. My face turned all red and hands swelled up and I could barely see. No real damage but it was very intense pain for a few hours and completely sucked. It also made me not like spicy food for about a year thereafter (fortunately that went away).
Off topic but just a word of warning about pressure cookers and hot peppers.
