What kind of cellar is this about?

A concrete cellar can be built to be waterproof. This requires an appropriate concrete mix, material thicknesses, sealing tapes, etc.
A [Weiße Wanne] is like a [Tempotaschentuch]. A type of waterproof cellar according to the WU guideline.

It is also possible to build a concrete cellar that does not meet the mentioned criteria but is additionally sealed (black coating).

Since the construction specification, which apparently consists of standard text modules and later describes deviations from the standard, refers to 17.5 cm concrete, I assume sealing with a black coating.

Ok great, then my assumption was correct, we will insist that it is not built according to [wu Richtlinien]

Huh?
Opening quote "We absolutely want a wise bathtub"

and now "ok we insist that it is not built according to WU guidelines"

I think you have not quite understood something.

What should the correct description be

If you want a basement as WW according to WU guidelines, then it should be stated like this.

But why? Because of the tightness against pressurized groundwater?
Both fulfill the purpose.

I think you didn't quite understand something there.

Typo: not "not", but "nach"

that it is built nach WU guidelines

Typo, I obviously meant that we want to build according to wu guidelines

We do not want this coating, you can read everywhere that the basement being coated does not have such durability