Yes, just like every digital video or image ever is developed to output on some sort of display. A still from the video doesn't automatically make it a screenshot. Particularly if it's not gathered by screen capturing methods.
What would you have me do? Download the video, open it in video editing software and extract a single frame? Is that what it takes to not be considered a screenshot by you guys, even though the end result will look nearly identical?
This is a screenshot. This is simply a single frame of video.
Perhaps your rules should clarify which is allowed and which isn't. You know, to avoid confusion.