Insufferable or ungrateful? Hardly, just expecting some accountability by the developer. Don't announce a release date if you know you can't meet it, it doesn't matter if it is free or not. I would be totally fine with NO date announced at all and just get the random alert that the new version has been released.
I get that the dev says that all dates are not set dates. If the dev knows that they can't meet the dates that they set forth, then why continue to announce a release date for the next update? Or if they are going to give a release date, they should give themselves a month or two buffer based on how every previous update has gone.