That's not a "rumour", it's conspiracy theory. Because everything is a conspiracy theory now.
No, the dosage is not patented. It doesn't even make sense. How would it work? "Oh, 0.5mg is patented, so let's put 1mg in the tablets and never sell 0.5mg".
I can get all kinds of dosages from the pharmacy. However, most of what they stock is "too high", probably because there's very little research/wisdom/knowledge around the supplement.