That's for previous Sony bodies.
Apparently things are very different with the A7R2.
Let's hope so. However Metabones own website doesn't make any such claims. I've seen one anecdotal comment at Dpreview of an example of a Canon lens used with the A7R2, which seemed to have an AF performance as good as the same lens used on a Canon body. But one can't draw conclusions from such isolated, non-scientific examples.
As I've mentioned, there seems to be a lot of 'hit and miss' issues when using an adapter. The Metabones website lists some the issues to be aware of. In particular, Canon lenses that predate 2006 might not work as expected. (My Canon 100-400 was bought in 2003).
Lenses that have some slight technical malfunction, perhaps due to a knock, which is not serious enough to noticeably affect performance on a Canon body, might noticeably affect performance when attached to a Metabones adapter, and so on.