I doubt whethewr you will ever be able to nail down an individual. The layout is based on the DIN standard below and was probably a committee decision.
The PC keyboard layout commonly used in Germany and Austria is based on one defined in an old (October 1988) version of the German standard DIN 2137-2.
If you really wish to pursue the individual/s concerned, a copy of DIN 2137-2 can be purchased here:
or I dare say your local library could get a copy.
To make your point - next time you write a letter, report or whatever to a German, swap the Zs and Ys all the way through!!