Not really. For one, China is still a totalitarian (communist is really wrongly used here) country. And also my impression is that Tymoshenko is more of an isolated case - my guess would be that most of the current post-totalitarian leaders are either former officers (Putin, Borissov, Basescu), humanitarian/law majors (Komorowski, Parvanov, Orban, Gasparovic) or economists (Havel).
Unfortunately most of them come from the first category :/
I don't know much about the other ones, but Havel most assuredly is not an economist. He has a cultural background and is an author of a number of theater pieces. His successor at the post of Czech president (Klaus) is an economist, so maybe that's where the confusion comes from.
Just as a matter of interest - the current Czech prime minister, who, at least in theory, has more power than the president, has graduated in physics, and has actually worked in research for some time. Angela Merkel (coming from Eastern Germany) has also a scientific background (in physics and chemistry).
But otherwise, it seems you are right about the fact that there is no such rule about post-totalitarian leaders being educated in engineering or sciences in general.
I stand corrected - just read that Havel has studied economcs for only two years before dropping out and that's probably the reason I have remembered him (wrongly) as an economist - I must have read it somewhere and it has probably stuck in my mind.
Btw, the rest of the Eastern European countries can learn a lot of things from the Czechs.
Unfortunately most of them come from the first category :/