Regarding the bike fit calculator, which of the three fit types would a 69 year old recreational rider choose as the basis for their setup? Eddy, Competitive or French?
I don't think its possible to predict to the cm what will work best for a given person. With given body dimensions, there's a range of sizes that can work, and the person has to set the bike up, try it out, and monitor his/her response. I'd start with asking, 'How close is your bike to the recommended measurements? Where's your discomfort?'
Millimeters may make big differences in your comfort, but I haven't come across any system that will predict what you will want down to the mm. You'll haveto experiment to find out which millimeters work best for you. Besides, I think fit changes through each season as our bodies acclimate to the riding we do. For example, I know I like my butt-handlebar distance now, but it sure felt like a stretch in April.
Once those questions are answered, you can make appropriate adjustments. When I was 69, my seat tube was plumb in the middle of one of the recos and everything else except seat-handlebars was French fit. Since different saddles have noses of different lengths, I can't see a point to seat-handlebar measurements.
I'd question any dogmatism I read. Bike fit is an experimental question. Almost any prescription you read on the 'net has to be taken with a grain of salt, except one which says something like 'almost any prescription you read has to be taken with a grain of salt - it may not work for you.'
For example, I'm a lot happier - I ride a lot farther and more safely - with pinned flat pedals than I was with 'clipless' pedals or with toe clips and straps.