Personally I will not be watching the film .... I find it distasteful that such a film should have been made in the Queen's lifetime. He was, after all her father. Would you want a film made about your father being instructed to say "Fuck" by some half baked quack, solely for the purpose of entertaining the masses?
As for the supposed reason for his stammer ~ that is pure conjecture. I have seen kids made to write with their right hand and whilst it never struck me as a sensible thing to do none of them developed a stutter.
Michael Palin made a very good plea for understanding in a film/programme about his own father's speech impediment that was shown on TV not so long ago. As I recall he did mention the late King's speech problem. I wonder if his sympathetic approach and the mention of the King was what triggered this particular bit of "factional"history making. The point is that the writers, directors and actors do NOT know the reality and it for certain that HM has not told them..... they can only guess so what they offer is assumptions, guesswork and fiction.
One other thought .... SWWLTBO is teaching Access Students History at a local college. Their original tutor was not a historian and her degree was not Humanities. Until she corrected them they were using the Kate Winslet/Leonardo What'isname film as a primary source for information about the sinking of the Titanic. FFS! It is not even a secondary source! I wonder how long before the same wooden headed students start quoting this film as a factual report.
Edit with PS ~ Sorry if the opening sounds a bit pompous but I really do have respect for the Queen and I do feel that she is entitled to some privacy and that should be extended to her late parents. At least observe the 100 year rule applied to the rest of us (see Census)