It is a sensitive issue. I think it is quite important to let people know where they can find drinking water on Teide, since there is none official, and during Covid not even the park office bothered to help people on this topic.
It is a legal and a budget issue, which is why they will never tag it as "drinkable". But I have used it many times and never got sick (until now).
I will tag the drinking_water as "untreated" and add the water_tap key, this is IMHO a good compromise.