I think they're intentionally vague when it comes to backorder dates as they don't have a concrete answer from Apple and don't want to set the wrong expectations. I wouldn't think it'd be more then a couple of weeks though.
@SamSam is pretty much right.
It's all about the expectation. The timeframe for backorders can range from two weeks to 6 weeks.
Apple is a tough one to nail down specific dates & timeframes.
Which model of the pro are you waiting on? Colour, capacity, size etc.
I ordered an iPad Pro a week ago and I was told by live chat that I will have to wait no more than a week for it to be shipped. Yet in my account I've had no new info about my order just the same wording about it is in progress. If nothing has changed by the 23rd I'll be demading answers. This is not how you are meant to treat new customers!
Which version of the Pro did you order @Ghost-Fox-Zero?
I might be able to give you a rough idea.