Sorry, it does NOT explicitly state that, you are making an assumption.
Just as assuming that "photos taken" means "all".
Better odds on that being true.
People don't use enough words in their writing anymore, which would help avoid any ambiguity, confusion, or mis-interpretation.
But a logical assumption. They don't want tens of thousands of unusable junk images to sift through. Which is exactly what they would get if ALL the attending photographers turned in ALL of their images. Including all the burst mode images, which generally have a per image low rate of usability.
They want the good shots that have potential for publishing.