okay, if we accept your thinking that Bairstow may be thought to be weaker against spin (though if that is the case, why take him at all?) should he not still be first choice once in more favourable conditions?
I think he's one for the future, so at the very least they'll have wanted him around the squad for the experience. Re picking him again, I guess that depends on how Root does here, but unless they think Root has similar problems on green seamers to JB on turning wickets then I don't think it makes sense. Horses for courses works to an extent but they need some element of consistency in the side.
All that said, I was still surprised to see Root in for this test, looks a decent call so far though.