Yep.
The H2O2 bottle even has the directions to use it as a gargle says mix with equal amounts of water for an oral abride solution, up to 4 times a day.
It is a bit of a throat clincher if you don’t add enough water though. I always have a glass of water standing by to immediately rinse and fill it again a few times - else I gag something terrible.
I suppose it whitens my teeth some - but I drink so much coffee and tea that it just stains again .