I think the idea is that this is for "left of the left" rather than mainstream left parties, which would still include Labour notwithstanding their current leadership.
It would also be a rather... er...
substantial misreading of the politics of the present leadership. Labour ran on a solid social democratic platform at this year's General Election not SEIZE THE COMMANDING HEIGHTS COMRADES and there has been precisely zero indication that this is likely to change (quite the opposite actually). In a weird and round-about way, Corbynism has turned out to be about the Left finally burying Bennism and moving on with its life.