Well, if nothing else, this thread has made me go do research and gain a new appreciation of Adelaide Crapsey and the cinquain, which before today I'd regarded as a quaint listing in my Poetry Handbook.
There's
a very nice essay with examples of her work I found, both of which I'd recommend. And I have to say I like Crapsey's original cinquains as well as I like any of the classic haikus, which is to say, I consider them interesting reflections on the world.
As for formally studying metrics, doing so is hardly a novelty, but the same as linguistics, is a perfectly legitimate field. In the end, what can be said is the same as many poets before her, Crapsey devised a form to her personal liking and taste and wrote the poems she wanted to in it--and dying of TB at thirty-six certainly gave her some inspiration--and the form struck enough folk as something they liked as well that it's continued, like sapphics and so on.
Though I think Crapsey's cinquains are scads better than the thing about the fireflies.