No confidentiality agreement (I've got no contact with bike manufacturers).
As for the info - it's a mix-match I gathered over the years.
Some of my own measurement, some from other mechanics, scarce official data I could find and similar.
It lived in txt documents and excell charts for some time, until a wiser friend convinced me to start publishing stuff online (and provided hosting for the first few years).
Publishing online provided a lot of help and feedback from enthusiasts and mechanics all over the world.
It also "forced" me to make the stuff more systematic.
Loads of updates and corrections over the years (I catch something, in some article, every month, that either needs update, addition or a correction).
Wasn't wise (long-sighted) enough to note all the details from the start.
Just wanted to have info about what I could mix and match (constant shortages of everything in my country
).
The upside is that most of the noted stuff is tried and confirmed in practice.
Tiagra shifters with "old-standard" 10-speed FD for example - a competitive cyclist friend was really eager to have it work fine, and it wouldn't work without a newer standard 11-speed FD (didn't go for a Tiagra once we figured a new FD is in store). I remember this for he had read my charts and came: "it won't work according to your charts, but could we give it a try?"
And I've been prudent enough to "hunt" for any discrepancies (i.e. if something does or doesn't work, while the existing charts state otherwise).
So it got improved over the years - and it lags a bit since I can't even see any really modern 1x12 and 1x13 (by rotor) stuff still.
edit - I wrote this "
Rotor 1x13 groupset review" without having even seen the stuff - LOL (as noted in the article)
TL/DR - it's a mess, not a really scientific method, but it works in practice.
Not sure I would have pulled it off otherwise, since it's a hobby, one-man show still (my day job is with computers
).
As I like to joke:
Theory is when everything is known, but nothing works.
Practice is when everything works, but no one knows why.
In Bike Gremlin garage, we combine theory and practice: nothing works, and no one knows why!