The whole "expending a markerlight token to launch a seeker missle" interrs that the model is in fact not shooting the seeker missle itself, but allowing the lazer lock guidence system guide the missle to the target.

Thus is fires at the BS 5 stated in the ability.

The model itself has to snap shot, but he isnt doing so for the seeker missle. He's expending the markerlight token to let the seeker missle go do its thing.