It's pretty close. The reason given was not that "the judge wanted to change the plea deal," but that the California courts couldn't prove to the Swiss satisfaction that the judge did NOT want to change the plea deal.
Here's the quote: "it was not possible to exclude with the necessary certainty that Roman Polanski had already served the sentence to which he was condemned at the time."
They changed the statement since I read it yesterday! The original version stated that: "... The reason for the decision lies in the fact that it was not possible to exclude with the necessary certainty a fault in the US extradition request, although the issue was thoroughly examined..."
I need to go and read the revised statement.