Apple’s offices were closed 22/12 - 01/01, which is a not-insignificant chunk of those 19 days (not mentioning that their chosen launch date was the first day back)
From Apple's announcement[1]:
> On average, 90% of submissions are reviewed in less than 24 hours. However, reviews may take a bit longer to complete from December 22 to 27.
It says on DHH’s blog. We can’t know for sure unless he shares a screenshot of it but more or less that is the reason because I was rejected with this same reason before.
>Of course we gave them a login. We’ve been publishing apps on the App Store for over a decade. This was not a low-level mistake. It went all the way to the app review board.
In another response he writes that the reviewers did in fact log in.