Most video's that are aimed towards piss are marked with "pissdrinking" Now largely this isn't the case. They block it with their tongue, don't swallow it etc... Only a selective selection actually engages more with the piss and swallows it readily. One example of this is Anastasia Mistress.
This is how piss drinking tag should be. Imo rather then fix the tags, fix the scenes with the models so they more readily engage with the piss and swallow it.