Hello @Gregor-M,
when you have a problem with bit depths, please open a new thread. This is now a bug thread and we should keep it clean.
What I forgot to mention here is that there is one way to sort of fix this right now for you. There is an undocumented flag named RDATA_BAKE_OCIO_VIEW_TRANSFORM_RENDER on the render data (not the same as RDATA_BAKE_OCIO_VIEW_TRANSFORM which is exposed in the UI tto the user). With that you can bake the full transform chain into the bitmap. Such bitmap will then be displayed correctly in the PV. But when you save it to disk, it will be "incorrect", as it got the view and display transform baked into it (which is usually not what you want).
But it could be an option if you only volatiely render documents for displaying purposes only or are okay with rendering things twice (once with the flag for displaying, and once without it for saving). But that is of course very much a hack why we will fix this.
Cheers,
Ferdinand