Is the first part of "A.I. Artificial Intelligence" based on Kubrick's or Spielberg's concepts/style?

I remember (99% sure) an interview with Spielberg (in a documentary of Kubrick's lifework), where he states that many critics falsely supposed that Spielberg was responsible for the first part (showing the life of the artificial child within its "family") of the movie, while the second part and end of the movie would rather match Kubrick's typical movie style. But, in fact it was the other way around, Spielberg said.

I'm aware the whole movie was based on Kubrick's script and concepts initally, but I would really like to know as a Kubrick fan, what parts of the final movie were elaborated by Kubrick's/Spielberg's views/style and why so many critics were wrong. Is the first part kind of untypical for Kubrick movie style?