Hi aagate
As you know, the somatypes are:
Endomorph: Large, heavy build, large boned and predisposed to carrying fat weight as well as muscle (often has sluggish metabolism).
Mesomorph: Medium build, generally lower fat compared to endomorph, but naturally carries weight and muscle in favourable amounts and position (average to higher metabolism).
Ectomorph: Naturally, slender and thin build with low muscle mass and fat mass. (Fast metabolism, pleanty of nervous energy to counter low muscle mass).
There are many varying definitions for the somatypes, and mine is just a basic description. Most individuals are a mixture of two somatypes rather than being wholly one type. Example: Some mesomorphs might have large bones and more fat around the waist than the total mesomorph. So the individual in this case is an endomesomorph (mixture of two). Most of us aren't exclusively one somatype.
The somatypes aren't really used as a descriptor or tool anymore. In the <1990's they were in vogue, and everyone's training was based around the presumption that you needed to train according to body type. While, somatypes are useful in somuch as a general description of someones natural build, they don't offer too much else. Of course, certain things apply to one somatype versus another, but they cannot be set in stone as we all respond to training and diet differently, and it's not all entirely fixed or dependant on solely your somatype.
I can't make any specific comments on what you've read or learned. You said, "according to everything I have learnt this is wrong."
Can you elaborate on this further?
Craig