I wouldn't say that everything that Ganin writes is crap, but that little article seems silly to me. Rather than make a case against it, I would like to see the case for it, since Ganin just writes it as describing his observations, which personally I can't confirm. What he's describing seems to be a change in a person's priorities, that is, getting less focused on pleasing a particular person (the reader of the article) as they feel more secure as they get to know you. That could apply to rational types too, if they are giving higher priority to something (or someone) else.

Anyway, although I do think rationality/irrationality can be used for typing people, in terms of behavior I think it's more useful to focus on temperaments.