If you are crouched or standing -> adjust your pose to be lower or higher (CTRL+S/W)
Try to reload
The stance will be changed to standard stand or crouch and will be changed back to low/high stance once the reloading is done.

What behaviour I would expect:
No forced change in stance while you reload, especially not in the lower stances since you usually lower your stance for a good reason (not getting your Head blown off).

A common scenario where the current behaviour is bad:
You are behind a low wall.
You can shoot over that wall while you are crouched.
You are in a firefight with the enemy.
You have to reload and you don´t want your head blown off while you do it.
You lower your stance (CTRL+S) so that your Head is not exposed.
Hit the reload key.
Oops your Head is back above the wall and may get blown off.