"Shaking it out"?

I've going to a small Asana practice in my neighborhood, I like em a lot. In one of my classes the instructor recommended shaking out after one of the poses, and I found it helpful since my hips feel so tight after that pose shaking feels useful for warding off potential cramps.

However, in a different class with a different instructor I was told not to shake because we are "building stamina". But how would shaking affect stamina? It seemed to me like the instructor just didn't like the disruption. It wasn't a big shake, just a little wiggle to get the blood flowing again. Anybody have a different perspective, were they power tripping or are there grounds to this?