Regarding the original question of the OP. The indication by the DJI APP is the same as those on most of the banking indicator used in real aircraft. I only learned it recently.
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Wait, what? No way!
Let's read that again. I think you're misinterpreting what that actually says. The horizon is always shown tilting as it should. They're not saying the horizon moves in the opposite direction on some instruments. They're saying the banking scale indicator confusingly moves in the opposite direction on some instruments.

I've never seen an indicator move in the opposite direction, so I'm only guessing at what that's actually supposed to mean. If you can find an example somewhere, that would help.
The diagrams you posted show the "Bank scale" delineating the angle of bank. I'm not sure why they labelled that mark as the "Pointer", as it's merely the zero degree mark on the bank angle scale. The actual "Indicator" is the orange triangle.
Normally the plane's wings (orange) and the triangular scale indicator (orange) are fixed and don't move. Picture those as being engraved on the glass cover of the instrument. Everything else, including the white lines of the Bank Scale move with the horizon behind those orange marks.

When the aircraft rolls to a 30° right bank, the orange wings and the orange triangle indicator stay fixed on the glass of the instrument. The horizon and the white scale markers roll left. It makes perfect sense that the indicator is now pointing at the Right side of the scale at the 30° mark.

Like I said, I've never actually seen an indicator move the opposite direction. The only way I could imagine that working is if instead the orange triangle indicator mark is now painted onto the moving portion of the horizon display, and the white lines of the Bank Scale are instead engraved on the glass face of the instrument.
In this manner, as the aircraft is again banked 30° to the right, the Bank Scale remains fixed but the orange bank indicator always points up at the sky and rolls left with the horizon. So even though the indicator is pointing at 30° toward the left half of the scale, it's actually indicating the aircraft rolling to the right.
Yup, I can certainly see how, "This may confuse the pilot..."
