Many thanks for your recording! I believe this is happening as you're not applying your changes/developing the RAW image before returning to Apple Photos. Unfortunately simply setting the sliders within the Develop Persona cannot be translated back to Apple Photos.
Please use Edit In Affinity Photo to open a RAW file from Photos in Affinity. Now, navigate to View > Show Context Toolbar and enable this option.
Now, set your sliders until you're happy with the image, then select Develop on the Context Toolbar. Once your image has been developed, you can use File>Save, then File>Close to send the image back to Photos, where it should replace the RAW file with the edited version. I hope this helps
Ron Levesque got a reaction from Dan C in Odd "Edit in Affinity Photo" behaviour