I didn't say that Labour wouldn't lose seats going more remain. What I said is that most decent polling analysis I've seen suggests they lose more seats going leave than they do remain. Because the loss of seats up North is overstated - because so many of their supporters did vote Remain.
As you say, 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 - and try to ride that ambiguity to Downing Street.
However I also believe that there's a deeper cynicism at play. As the Guardian published bits from a report shown to the Shadow Cabinet about not going full remain with an exaggerated loss of Northern seats that most polling people I'd read didn't believe the polls agreed with. Corbyn's team are possibly leavers - trying to delay their own party from backing remain until it was too late - despite members being 90% remain and despite his pledge that he believed in bringing back internal party democracy. Or they didn't really care that much about it, but wanted leave to happen on Tory watch, hoping for a disaster so they could have a landslide and bring in "proper socialism" red in tooth and claw.
That's broadly my opinion - a sort of a combination of the two. That a clique of the hard left, quite a few of them revolutionary socialists who want to overthrow capitalism care more about that than anything else, and have successfully captured a major party to do it. Corbyn is of the fluffier Bennite persuasion, but as Tony Benn said, "there should be no enemies on the left". i.e. allying with communists is OK, because at least they're not evil Tories. So even as a generally Conservative voter, I feel quite sorry for ordinary Labour Party members - because they've been put in a really difficult situation, and they lose all chance of getting the policies they want on Brexit (which they deeply care about) - because they let their party be taken over.