That video kinda is weird to me, if you are rolling left, then the (any) gimbal tilt should be the other way . . . at least it is on my MP when it may appear with overly sharp stick movements.
Same as if you were hovering and there is a very stiff breeze coming from your left, the drone is pitched slightly that way, it usually shows with tilt towards the pitch direction, if the breeze gusts etc.
Yours almost seems like an over correction the opposite way.
Wouldn't you know it, I just looked through the Photo / Video section for an example, couldn't find one in 10 viewed, so found one of mine on YouTube
Check this at 0:45 as I start a roll / yaw around to the left, I get a little horizon tilt . . . it was also blowing pretty hard from the back before turning, so it came onto the left side as well through that turn.
But that is the way you expect a gimbal to tilt.
Your example video shows the opposite gimbal movement, so I wonder if it is over correction happening.