The problem is with his left foot!
He’s setting up to throw in an exaggerated wide stance. His left foot is extended way too far and that drops his center of gravity significantly (and with it, the release point).
It’s simple physics.
Over-striding also locks up the hips and minimizes the rotation needed to put velocity into the throw. And it can cause the back shoulder to dip, causing the ball to sail.
Basically nothing good happens when you overstride.
From the reports Tanner is performing well in spite of this so I don’t know if it’s something to obsess about.
Personally I’m more concerned about his ability to make reads efficiently. So many of the clips I’ve seen from fall camp show him dumping to the RB after he’s gone through maybe two checks.
He seems to panic more than Wilson.
Then again who knows what’s happening in the closed sessions.