I know my position pretty well in a general sense, not specifically for one bike tweeked in. I ride about the same position now on a performance bike as I did in 1974. The devil is in all those pesky details. I go to the details, then change something, and back to the details. Changing something being a 5 mm change in stem, knocking the saddle fore and aft a bit.
I notice that on fairly upright, mellow riding bikes my fit needs aren't too demanding. I can get on and ride, move a few things and be happy. I ride with my feet forward on the pedals for mellow bikes.
The higher performance the machine, the more I find I want to get something special out of it. Takes much longer to get the details going. And each machine seems to like something a bit different to get me comfortable on it. I can't see how one set of numbers is going to do more than getting in the general ball park. Given that that I've been perfectly comfortable on good well fitted bikes with a 1.5 cm difference in fore and aft saddle position relative to crank, I have to wonder how 1 particular position will be very close to ideal for one bike. If I have high bars for touring, my saddle ends up back a bit. If I have the bars down, then the saddle ends up forward.
And that's just the general fit. Current bike, I rode a few months, then decided I was getting understeer just a bit and and wasn't comfortable in my arms. Narrower bars first. Moved them up and down. Still wasn't quite comfortable or locked in. Slipped the saddle forward a few mm. Better, then I started to get cramped shoulders. Longer stem. Back and forth on the saddle. Then change the bar angle and click. In the zone well enough to start fine tuning. Now the machine feels good and handles great. And the position is substantially different from the previous one (still set up) that feels fine, but is a high-bar fast cruising setup, rather than a cranking fast handling setup.
How on earth is a number machine going to do anything but get sort of in the general ballpark? And for what style of riding? Over what terrain? If I'm going to ride across the midwest I'll use a different setup than for bashing over our Appalachian hills.
A good eye watching position on the road and making recommendations might be better than any fit system. The road is different from a trainer.