I saw it myself and I thought it is a bug at first, see my "Culture being bugged" thread from Saturday. But now i think it is not, its supposed to work this way.
I think its going to be viable for multiplayer on ICO as well, as i had hard time dealing with culture spread by AI myself. I had to dedicate literally entire planet to culture centers to stop losing allegiance on nearby planet and i can imagine if this culture planet of mine was one more jump away than it was, i would have had a problem.
What i am trying to say, as the planet specialization is irreversible process, you need to think twice now, which path to choose. It may as well happen, that you choose industrial, while your enemy on neighbouring planet chooses social - and you wont be able to stop the culture spreading from there no matter what. Building just culture centers to push it back wont work anymore. That is at least my impression from a game i played on Saturday.