"Corbyn's strategy has been the deeply cynical one of trying to have no policy on the biggest issue in British politics in a generation"
No, Corbyn basically shares the ERG view on Brexit, except he thinks they're a bit liberal on trade. He has been muzzled by his advisers because admitting that would seriously threaten his tenure as leader. But it's been widely covered nonetheless.
Even taking it at face value, Corbynism is illegal under EU law in too many ways to count. Brexit is fundamental to a Corbynist government.