I recently had a question relating to video conversion where the input format was OpenEXR and I used ExifTool for diagnostics. I think these would make helpful tags.
I'm not sure I see enough of a case for ExifTools specifically. On EXR, is there really enough of a difference between EXR and OpenEXR to make it worth its own tag? I've not personally worked with EXR, but it sounds like OpenEXR is just one particular implementation of an EXR encoder. I'm not sure that is worth a specific tag either.