Got it. Thank you for the help regardless! The linear to sRGB transformation did seem to work.

Yes, color management is not applied as confirmed by this post: https://stackoverflow.com/questions/65719891/pixels-retrieved-from-viewer-node-within-blender-are-darker-than-the-actually-re. That is the bug/new feature I am reporting since it is impossible to retrieve any correctly colored render image without writing it to disk first.