I feel like the variation in people's knowledge of Socionics is too great for us to accurately say what type is a good person-who-does-that-typing-thing. In the sense that there are some people who seem to know Socionics better and have more experience and have known a greater variety of types and examples of those types so they can drill down faster and are more interested in the theory so they can understand different aspects which in their minds justifies what types are what and they think about the theory more often specifically how people relate to certain types so they just have that kind of information in their memory, etc.
Any attempts to point at people and say "I think they're a good typer," is probably not going to be very fruitful as the reasons why they're a good typer can't really be shown using information element analysis, and so are subject to other factors (maybe certain types take to Socionics more? Again, I don't know). I believe.
What a dull response.