This type of UI inconsistency is very common in betas of a major release. It’s not uncommon for them to even make their way into a final release.Actually, there is an inconsistency going on with these leaks. First, the dock has a darker tint, then on the taken screenshot, it's lighter.
That being said, it’s a little off that they were able to capture a screenshot of the dark dock once (in the first screenshot) but not in the 3rd. That seems fishy.