Or the pictures taken with Pegg and Yelchin were taken earlier, just as the last scene in production was being filmed.I was thinking the same thing...We don't even know why they're wearing those uniforms. Let's not judge too quickly.
Most of those pictures were obviously taken NOT during filming. The story even says many of those pictures were taken at the "cast farewell party" after principle photography was complete. So, even though I have no idea why Yelchin and Pegg would be wearing uniforms if not as movie wardrobe, there is a chance those uniforms were NOT pieces of movie wardrobe.
Maybe they were wearing those as some sort of cast wrap-party joke, or maybe a little cast party skit that Pegg and Yelchin performed, just for fun.
Exactly...We simply don't know.