I point to the poll results of Jolla where 405 people of 983 voted for 5”. This is the main fact for the discussion and the one I mentioned right from the start. And the only assumption here is that this is a unique parameter for many of those voters and they would only buy smaller than 6” phone, so this is a deal breaker.
3% of iphone sales? Seems to be about right, this is at least 6 million phones per year, and here Jolla aims to sell at least 2 thousand.