Images are not sharp on retina display

[kolibril13]

Screen.Recording.2022-06-22.at.17.24.24.mov

Video cells explained:
Cell2: unsharp splitview plot
Cell3: unsharp Matplotlib plot
Cell4: sharp Matplotlib plot
Cell5: still unsharp, but larger splitview plot

When changing to %config InlineBackend.figure_format = 'retina', then the images are displayed larger in the splitview image, but not sharper.
Here is the corresponding notebook: https://github.com/kolibril13/jupyter-splitview/blob/6ea5f6b7a3487e324d0f9d2d50651919cb309bd6/debugging_notebooks/bug_retina_display.ipynb