I don't want to get too deeply into this because I would have to reacquaint myself with the reports. But my recollection is that even Warren's own staffers sided with Sanders' version of the events, that no one confirmed Warren's version, and that Sanders' version was the only one that was remotely consistent with his past actions (namely, urging Warren to run in the previous cycle). Yet Warren confirmed on the stage (iirc) her claim that Sanders flat out said "a woman can't win."
I kind of expected to drift toward your position (that it wasn't a big deal) over time. But, more than a year later, it still strikes me as a particularly toxic and unseemly thing: to purposefully leak a report like that, which has no bearing on policy but rather is specifically aimed at an opponent's character, in a pivotal point in a race and to then more or less refuse to engage the topic and instead feign indignation.