And let's remember that Gorilla Man's shirt is not even sprawled open like Doorman's. They forgot about doing that.
And the fact is that his shirt wouldn't have done that anyway. What we are seeing on Doorman is the result of the combination of it being an unusual shirt, from Russia, with a soft collar and soft placket, and the fact that Oswald had lost weight; the shirt was too big for him, and he was swimming it. Even if they had remembered to unbutton Gorilla Man's shirt, it wouldn't have looked like what we see on Doorman.