I'm gonna guess it is not "legit". Meaning, that if CO knew you were willingly purchasing the ticket and not using the service they would void the miles.

That doesn't however, mean you can't get away with it.

You would probably just have to submit the ticket as part of a "missing milage request" further down the road.

For future reference: An FTer's have direct experience with the "don't even board the train and just submit your stub" technique?