What this means is that in comparison with all other existing methods of Type identification, V.I. is the fastest and most reliable (in comparison!). And of course it is not 100% bullet proof. Even the experts can make mistakes using V.I. So imagine what the other methods are like in comparison - the Stone Age!
Fair enough... of course meeting someone in person after gaining a thorough understanding of Socionic theory will be more accurate than subjective testing, writing analysis, and the like.

Glasses, hats, makeup, plastic surgeries, photo manipulations can throw even the expert off course. This is why it is necessary to have more information about a person than a single photo. A video, for example, already contains tons and tons of useful information. Meeting someone in person is highly recommended.
Nota bene, it seems. I guess we're really meant to take note that by V.I., he truly means "visual identification" <- in real-time, in person. This only confirms what I have believed that V.I. by means of still photography just isn't an accurate or plausible means of identifying type - especially on a board like this, where we've got so varied a public; some people here are working through mere guesswork, others by pseudo-phrenology, still some through means of MBTI... interestingly, on that very website, check out that V.I. skills test <- what do they give you to work with? No prior knowledge and a whole lot of ugly drawings...