That is interesting, I am curious how that works too. At first I was going to guess that maybe some of your oscillators were not tagged as such--I have seen many modules in the database which are not tagged with all of their functions. But all of those in your rack are marked as "oscillator", so that can't be it.

I wonder if it does the calculation not by the number of modules, but the number of functions instead?

As a really simplistic example: Suppose we have a rack with only two modules in it: a Behringer Brains and a Wasp filter. If we're counting by the number of modules we have one oscillator out of two total, so 50% oscillator. However, if we are counting by function instead we have one oscillator out of a total of 5 functions: Drum, Noise, Oscillator, and Synth Voice from Brains + Filter from the Wasp. That calculation gives 20% oscillator.