He would need the support of some of his party, and of Labour too, but can you imagine the blowback if Labour said no?
If BJ were successful, that would mean that there was no Parliament constituted all the way to the end of October and beyond.
By doing it this way, BJ would force Labour to choose no deal Brexit or political suicide.
Labour's number 1 preference is a GE. Alright, says BJ, have one!
Maybe it would drastically shake up politics. But in doing so it will have also delivered the worse possible Brexit outcome.
Or GE on 7 November (Parliament dissolved on 4 October)
He might see the latter as (slightly) more diplomatic.