This is simply not true. They made it perfectly clear that they wanted a deal with the customs union and single market.
>True enough -- to a point. But he could say what the general outline of the UK's goals in the negotiations will be and how the strategy/objectives/redlines will differ from TM's and Boris's.
Could and did. The media has done a grand job of obfuscation about this despite the fact that it was right there in the manifesto.
>He cannot say for certain how the EU will respond to any proposal, although honestly Barnier has been crystal clear about what is required of the UK and what the options are.
What Barnier has been less clear about is whether they are prepared to negotiate a new deal at all after May's deal. The EU actually has flip flopped on that issue and its mind probably still isn't made up even now.
>And does Corbyn even know the difference between the Single Market and Customs Union? I have seen no indication that he does.
I suppose you have seen an indication that he doesn't?