I've come to the conclusion that the cell size issue has come to be such a point of contention because of our scientifically minded culture. It's the same with some religious, political, and social issues. Scientific study is very very often simplified by making assumptions and removing variables so that the study can be based on just one or a couple variables and not all of them. It's those simplifying assumptions that really lead the science based in the natural world to useful conclusions and productive innovations.
I am intimately familiar with these constructs as a civil engineer. I just finished a five page spreadsheet for the design of an aeration basin for a waste water treatment plant, and I'd dare to say 3-4 pages of that was based on assumptions made because actually testing for those parameters would be prohibitively expensive. In this type of engineering and especially with foundation engineering, factors of safety can be applied which smooths out the problems that may exist in the design due to simplifying assumptions.
As far as I know, there are no factors of safety in beekeeping (except maybe in the amount of honey one leaves for winter). I submit that in scientifically based beekeeping studies, the simplifying assumptions are what causes much of the strife between the treating and not-treating crowds. Yes, the studies show that small cell doesn't help, but again it comes to the simplifying assumptions. None of the studies tested under real world conditions, over the space of years like actual beekeepers keep bees. I hope Michael Bush will explain it because he can do it better than me.
One of the simplifying assumptions is that the number 4.9 means anything. It doesn't. It's just a number. It's an average. Averages are mathematical constructs, just like wind chill. They don't actually exist. They are a fabrication of mankind to make another simplifying assumption. 4.9 is useful for understanding the issue, to achieve a sense of perspective, but beyond that, it's useless. We all know for a fact naturally, bees build a range of cell sizes. So the idea of having a magic 4.9 number has very limited application. We choose not to make foundation rollers with a range of cell sizes, another simplifying assumption. I'm sure it's possible, but it would be a pain.
It's like when Oldtimer was doing his experiment and he found out that his foundation was 5.0mm and not 4.9mm. He was concerned because he seemed to feel that he wasn't reaching his goal of real small cell beekeeping. It was my position that it wasn't that big of a deal.
But here are the realities. Cell size isn't the only variable. Having exactly 4.9mm cells isn't the only answer. Dee said it was a combination of cell size, genetics, and management. Kirk Webster says that a collapse and recovery is necessary.
http://www.kirkwebster.com/index.php/collapse-and-recovery-the-gateway-to-treatment-free-beekeeping A big part of it is raising your own queens. I have always said that you had to lose a bunch of bees and expand up from the survivors. I only wish I had more time to be intense about it. One of the overriding problems in my view is that most people don't seem willing to lose a hive if they can at all help it. They always want to help. They always want a simple solution.
But as has been proven, there are no simple answers. Treatment-free beekeeping is simple in concept (don't treat, expand from survivors) but truly understanding and implementing it is complex and difficult. Thus far, there are relatively few willing to do it. It's like I tell my tutoring students: "They don't pay you good money to do easy stuff."