Yes. The whole Redweek "online booking process" which necessarily includes the verification process as well as the online booking procedure must take so much time that they need at least 21 days.
I have in the past had a last minute change that necessitated my attempt to rent the week out via Redweek. And I saw no such banner. But, in that case, I didn't do the V&P route.
And in the past when I did the V&P route, I saw no such banner because my ad was placed many months before the check-in date.
So I personally don't know if that banner always arose in the past if someone were to have tried both (1) the V&P route and (2) check-in date within 21 days, but mauiwowie's post above seems to suggest that is a change. But maybe he/she was always a DIY renter in the past.