I don't think it would change with a browser. I've seen similar things with different articles of clothing. I think it's just the way the clothes are layered.
The layering would definitely make more sense if the sleeves were under the coats though.
I have always and can still layer a jacket over long and short-sleeved shirts, so it does seem to be a dress issue. Not likely to try them all on, but I will check out some more.
Additionally, I cannot get any shirt sleeves to show from under the hot dog costume thought they have no sleeves at all.
ETA: Tried layering under the sushi costumes as well. Sleeves not possible. Maybe costumes are supposed to be this way. Yet dress sleeve DO show from beneath costumes.