Scaling was set to "Sharper". And yes, it's present in the render.
With scaling set to "sharper" or "smoother" the output is like this :

With scaling set to "bicubic" or "bilinear" the output is like this : (no "black" but still stair case)

If I either :
- In any scaling mode, I crop 1 pixel on the top.
- Or in "sharper" or "smoother", I add a fusion comp on the top clip (empty one, just go to fusion tab, move the node, go back to edit tab). For the "bicubic" / "bilinear" mode, adding the fusion comp doesn't change the result, still white staircase as above.
Then the result is like this : (which is what I would expect)

Resolve Studio - Ryzen 5800X3D - AMD RX6600 / NVidia RTX 4070 (switching between the 2) - Linux