This is advisory; it is not law.
Makes sense, sure. When you jump into a new plane, you need to find out which knobs and dials do what
Nobody sensible disputes that.
The debate is wholly concerned with where the line is drawn to (a) suggest and (b) mandate specific training.
Under ICAO you have the old Type Ratings and Class Ratings which formalise training at specific levels. Some of this is rather contrived e.g. the "complex" category triggered by a CS prop or retractable gear, both of which are completely trivial compared to some modern avionics which, frankly, a lot of people would not get their head around unless they get a
lot of training of which none is mandatory.
A TR for a plane above 5700kg is equally contrived. It's just a line in the sand. The plane itself might be really simple and easy to fly.