My final conclusion on this is that i'm going to have to go with this just being a smear tactic from the Warren campaign about an intentionally misrepresented statement Sanders said to Warren in their meeting 2 years ago to get some attempted momentum going into the debates and voting. I've tried to hypothetically think about Sanders outright saying to Warren that she outright just cant win, because she's a woman(especially with Warren just sitting there and taking it while going on to make an alliance for a while) and it just doesnt square at all.
Unfortunately, with the "his volunteers are going out there to trash me by highlighting accurately my and other candidates base of support to voters as an electoral strategy", i can absolutely see Warren reluctantly going along with a plan with her team to 'leak' a story like this and then vagely try and equivocate on it so the team itself doesnt have to directly say "he said i/a woman cant be president" instead of "he was highlighting the challenges trump would pose to a female candidate rather than saying a woman or her could not outright win".
When even Washington Post who i would not trust as much as i can throw them is saying they have sources(what is with the anonymous sources) claiming that the latter was the case, its really just a dirty situation.
After all, on the face of it the charge doesnt make sense when he directly supported and saw what Clinton could have done and she was probably one of the worst representations of a female candidate. Imagine an actual good one. Not to mention his statements and record, and if you dont want to take that into account, we know that he wanted Warren to run against Clinton to beat the centrist wing of the party originally before he was even known nationally, which blows up the whole argument.
I dont think this was originally her idea but she hesitantly went along with something her staffers did to try and help her poll numbers for political purposes. Unfortunately, warren has a habit of doing things for political reasons and being really transparent about it..whether it comes to falsely equivocating about M4A and how her kids went to public schools(they went to private schools) to seem more 'down to earth', nothing is more illuminating than taking the identity of a besieged group of people like Native Americans for years and then doing and saying absolutely zero when they needed help with Standing Rock until after the fact when there were plenty of other progressives who proudly called out that injustice. Apologize for claiming Native American ancestry indeed.
Its just a really shitty situation in general, but people will still go to their corners on this one since its "he said she said" bullshit, which only helps Biden and ultimately Trump. The media will do their thing for a few days and that will be that.