Thanks, and no need to be sorry. Neither is my idea to argue with you. This is a fruitful discussion which I believe will be of interest to other users as well.
I think that the key here is the word normalized on the magnitude axis. Looking at the plots, it seems like normalized magnitude applies the scaling necessary to make the maximum magnitude 1. With such normalization, dB makes perfect sense! Also, with normalized magnitude in the axis label, the risk of confusion is more or less eliminated.
At the moment, this type of FFT plot cannot be made with SystemModeler, but if you have access to Mathematica, you can always run your simulations with
WSMSimulate and then use
Normalize (with the infinity norm expressed using
Norm) and the rich plotting capabilities of Mathematica to obtain a normalized FFT plot.
Thanks again for clarifying your suggestion. Your feedback is valuable.