Have they actually said they're picking him because of some disruption he causes? I've never seen that.You’ve got to weigh up whether its output and nett result is going to be greater than the alternative.
The obvious comparison for now is, and will always be, England.
England have decided that a very mediocre batsman like Crawley (let’s leave Duckett aside because his 40 average is decent enough to earn him a spot regardless of how he does it) can keep a spot because the ‘disruption’ he causes to the opposition when he lasts more than a few overs is worth more than the few extra runs a more sedate batsman might average than Crawley’s bog-ordinary 33 or whatever it is.
They think that the 1 test every 3 or 4 that he might set up for them at 0-80 after 12 overs is worth the pain of the other 2-3 where he leaves them 1-10 after 2 overs every time he goes out to bat.
If they want him to do that they need to balance out what they think the minimum pay off is
What I have seen them say is that the pick him because of the potential peak he can provide, which while rare is excellent, and the expectation that he will love the pace and bounce on our pitches - which is crucial as England basically live from Ashes cycle to Ashes cycle as opposed to just playing what's in front of them, like everyone else does.