It's about the control-output measurement of a flyback converter with multiple outputs. The point is to show how theory and practice don't line up with each other, and you ultimately have to design based on empirical measurements.
Multiple Output Flyback Converter
In this case, the control-output transfer function has an unusual slope somewhere in between -20 dB/decade and -40 dB/decade, when it should just be -20 dB/decade.
I've seen this effect repeatedly over 30 years of making measurements. You don't see many papers on modeling multiple output converters because it is tough to write a research paper when the theory falls apart. However, this is reality, and we often have to design with what we've got, not what the simulation software says we should have.
The data shown in this paper is really just the tip of the iceberg of of how weird multiple converters can get. One of the more interesting cases I encountered was a situation where the loop design was determined by the esr of a small rectifier diode which caused an unintended 30 dB extra gain at the crossover frequency.