Ma6 is a fill. It's a I variation or a I vi, with I (or i) in the bass. I just don't look at keys anymore. It's a means of notating. Which honestly, is how most music is written, nowadays. You have to know your stuff, before you can be hired, especially in lucrative studio session playing.
One can look at this in many ways. Be open. I steal from very innovative players. My knowledge didn't come without very, very hard work. You may see something new in just, simplicity.
A lie goes around the world before the truth gets it's shoes on. (Mark Twain)