Your plates can be washed with temperatures that would scald you and with chemicals that dissolve your skin.
But you don’t want to sanitise your skin, just get the dirt off, so I don’t see any real issues.
And your colon lining if not washed away thoroughly
The issue is that water would be so dirty and gross. The same water that washed your rear end will then be sprayed on your face. If you are only using a few gallons (not like a bath which has dozens) that's pretty gnarly.