some of the posters have very well tailored jackets, and raising their arms doesn't raise the bottom of the suit. I believe that is what they are doing, and you are refering to. I may be wrong, of course.
That pose is what educates the lesser knowledgable folk about what high or the correct armhole height should be.
"Looks like a penguin"....if you did it with low armholes you would look like a bat or a flying fox.