It was a definite message by someone.
Given the average democrat thinks all guns are assault rifles, and use “clips” and “magazines” interchageably, I can see that some people there probably would not have noticed. I am convinced however the higher ups running the convention knew and wanted this shown this way.
I’m more inclined to think some radical red Junior Woodchuck assigned to make the vid thought it would be cute to slip that into the presentation as a poke in the eye to the US and conservatives in particular.