♭IImaj7 and ♭vii7 combined

These two chords are variants of each other. Play the previous two vamps yourself a bit when you get a chance. What you’ll find is that ♭vii7 and ♭IImaj7 sound like two sides of the same coin, two interpretations of the same underlying sound.

And so, musicians often take advantage of this to make variations on this theme.