I sort of agree with you on this, but not completely in that I think extreme personality disorders can warp personality type. For instance, I do think psychopaths can be typed, but the psychopathic version of that type is very different than the normal version of that type. So if you get a psychopathic SLI and a normal SLI then they will behave very differently and think very differently, but they will both be SLI. So Socionics somehow manages to fit two very different people into the same type and this is the problem with Socionics, you can fit a lot of different people into each of the 16 boxes.
Let's just say without getting into too much detail that from personal experience I get along a lot better with the normal SLIs than the psychopathic SLIs for obvious reasons. Since it's been brought up, this is how believing Socionics blindly is dangerous because you don't want to get into a relationship with your dual if they happen to have an extreme personality disorder like psychopathy if you are not psychopathic yourself or have something that can get along with it. Since it will take someone of a compatible mindset, not necessarily the same to get along with them.
Socionics only covers how we interact with other people and the environment around us, but it completely ignores other aspects that can affect our personality and how we interact with others like empathy, general intelligence, social intelligence, personality disorders and the list goes on really. These non-Socionoics factors also have an ITR of their own like certain personality disorders getting along better with other personality disorders. So when you are interacting with others, these non-Socionics factors should have equal if not greater value than Socionics type since Socionics type merely covers one aspect of a person's personality and how they relate to others.