If you want to learn to strum properly with good time first then see some of my recommendations that I personally have found that work if you practice.
Its important to not bite off more than you can chew and to make realistic goals. Robben is voice leading with chords and admits himself he started out playing jazz guitar from a Mickey Baker book.
He talks about knowing the pentatonic scale and playing thirds as his whole style but its more than that. In the section they do have at the end called Right Hand Control, he talks about steady right hand strumming and downstrokes and calls it a real evenness which he has never thought about before and he repeats he is making this up as he goes. How that will help your rhythm is debatable and even questionable. Love you Robben but you are a just little too pleased with your own bad sef.
This following recommendation of mine is what you should consider if you want a real value filled, blues rhythm guitar jolt of caffeine: Shun Kikutas Great Chicago Blues Licks it blows this particular guitar lesson away as far as real blues is concerned. Among a lot of other blues guitar technique Shun shows you the three dollar chords Robben uses for jazz but Shun uses them for blues! A Japanese kid with a Berklee Music Degree. I kid you not. One of the best lessons on the site!
Start by doing what's necessary; then do what's possible; and suddenly you are doing the impossible.
Francis of Assisi