Thanks for the video. The scroll is not a proper Band scroll. It simply scrolls the whole screen with a Partial window.
Partial Screens are fairly useless feature of most TFT controllers.
The ILI9320 style supports two Partial windows that you can move around the screen.
ST7781 has two Partial Windows in theory but does not work properly.
ST7781 hardware actually has Vertical Scroll but it is broken. Hence no mention in the datasheet.
S6D0139 has two Partial Windows but no ability to move around the screen.
Most MIPI controllers e.g. ILI9341 have a single Partial screen but no ability to move around the screen
I have amended test_0139 on GitHub. Please try the regular graphictest_kbv example.
You should see whole screen scroll. The "Band scroll" should move the whole screen too. i.e. like a ILI9320
David.