I think it's because you've got Bairstow now in the top six but still keeping wicket which looks a potential weakness, plus then Moeen who, particularly at this stage in his career and with licence to swing at it, looks good for a nice looking 15-20 most likely. They're both a place too high I'd say (or Bairstow would be fine with Foakes keeping at seven).
It looks to me like the extra bowler has been crowbarred in a bit because they don't trust the fitness of Stokes and/or Moeen to bowl.
ETA: It's Woakes who stands out as a bit of a fudged selection I think. It looks like they're hoping he can do enough batting and bowling to just about cover for the gaps elsewhere IMO.