Cummings detests Farage, his strategy of 'do or die' Brexit by the 31st Oct was also to neuter Farage and the Brexit Party once and for all, make him totally irrelevant politically. That's now failed with the extension Bill, so they have to change tack somehow and get a deal before the 31st in order to nullify Farage. A majority of Tory members when polled over the summer were happy to see the break up of the Union if it meant Brexit, so a Northern Ireland only backstop wouldn't upset them, just the DUP, who at the moment are useless to Johnson as their votes make no difference anymore. So, why not throw the DUP under the Brexit bus while parliament is shut down for 5 weeks and then vote on May's deal with a NI only backstop when they get back on 14th Oct? Numbers would be tight with some ERG voting with DUP against it, but some Labour also likely to vote for it...