IT IS POSSIBLE!! Sort of..
You can select the photos, + them into an album, and then archive them! (Found in the menu at the top right while selected).
Unfortunately there is no way to easily see which photos you have already sorted into folders so you'll have to do them all again and forever really… but hopefully this helps a little! It has for me :)
You can also just sort photos from the albums' on your device by going to Albums then your Camera album. Select the photos you want moved and then DO NOT use the +, instead select the menu in the top right corner and then Move to folder.
The + is just tagging the photo to an album without moving it. I don't think sorting them in this way takes them out of your main Google photos though so keep in mind it is separate.
