That was the claim made in post #2 of this thread, and has not so far been refuted. If it is actually incorrect, and all the production boards are in fact 4-layer as in the published design files, perhaps this would be a good opportunity to get that cleared up right away.
When we finally get a set of definitive and up-to-date design docs, and ideally also a list of errata where there are known production variations from the reference design, we will all be on solid ground, and in a situation that such misinformation would not be able to proliferate.
As it is, it is a bit disturbing that no-one can confidently say how many layers the board they have in their hands is!