Blue Bossa progression (but I'm wrong, and it still works)

Started learning Blue Bossa today, so I always start with the chord progression and jam around with no backing track with chords and scale only. I noticed afterwards that I was playing BbMaj7 instead of Bb7, but somehow both A and B natural notes work in the whole context.

Hope you enjoy it!

Видео Blue Bossa progression (but I'm wrong, and it still works) канала Adam SQ5VCO