Can't access RAW files in Photos.app
Ok, the problem is one of:


The Photos UI is very poorly designed.
I am a dummy


Or a combination of the above 

The Use RAW as Original option is only available when you are in Edit mode and only affects one photo at a time ‍♂️

Related:


  If I create a Smart Album with Photo is RAW as the only criterion, it only shows me a fraction of all my RAW files (170 images).


This is because the is RAW criterion isn't if a RAW file is available, rather, if a photo has previously been switched to Use RAW as Original