Each lighter may be of stronger or weaker metal.
I think they were using the kind of lighter specified in the myth, though.
What surprised me is that there's cotton inside the lighter. Although now that I think about it, I suppose it makes sense. I figured a lighter just had a hollow space inside for holding the fluid, but I guess there would need to be some kind of wick connecting the fluid to the flame no matter how low the fluid level gets. I guess that's what the cotton would be for.
Sure, I know there are treaties banning aboveground nuclear tests, but hey, President Obama said he wanted them to let him blow something up, so maybe he could've pulled some strings.... 
