Not a Mac user so just guessing that this is what's happening here, but the message you showed says you need to make the files writable. To me as a Windows guy that implies the original files are marked read-only. I doubt this is actually related to the applying the edits of one photo to other photos process. Since CR2 is a raw file that makes sense, since you don't ever want to actually write any changes into your original camera raw files and read-only protects them from changes. (Lightroom "edits" are non-destructive - they are not changing the original file but instead are saved in the database or sidecar files while the original raw file remains untouched.) If you try to export the original CR2 files with editing changes applied to them, the original files are copied and then the edits need to be written from the database into the copies, but that can't happen if they're read-only. Exporting as TIFF or PSD, on the other hand, works okay because it's saving a new file instead of trying to replace an old version with a new one. "Export as original" would be doing just what it says, just making a copy to a new location of the original file as it came from the camera. I'll bet if you explore the file attirbutes of your originals outside of Lightroom you'll see that they have the read-only attribute turned on. Turn it off and I bet you'd now be able to complete your export of those files with the editing changes in place. Now as to whether that is a good idea, that is another story. IMHO, there is no reason to actually write edits into the raw file. If you're doing so in order to preserve them for a move over to Photoshop or some other image editing sotware, go ahead and use TIFF, if you send it as a CR2 it'll just have to be converted to something else in the editor anyway. Same if you're doing it to archive the files outside of LR once you're done with them - nothing wrong with using LR as your archive, leaving them there in the LR database, but if for some reason you don't want to do that, exporting them as TIFF and archiving BOTH files, the original virgin CR2 and the edited TIFF version is much safer. After all, you never know when you might want to go back to the original as-shot file and start over editing from scratch.
