Rectified tiles or calibrated tiles or standard?

This is all shake-your-head stuff! The term "anhydrite screed" is outdated, has long since ceased to be part of the technical terminology, and has been referred to as "calcium sulfate screed" (CAS) since 2003. The fact that calcium sulfate screeds "attract water" is basically correct when considering the material-specific sorption isotherm, but it is rather academic in nature. Cement screeds become damp at about 65% to 70% relative humidity, while CAS screeds only above 85%, and then only marginally. A screed is also not ground for the purpose of achieving load-bearing capacity. Because screeds, no matter how they are installed, are not load-bearing (and therefore not a static) component! Nor can load-bearing capacity be created by material removal, as grinding represents, only the readiness for laying in terms of the surface strength of the laying substrate. I privately note that the tiler has probably not fulfilled a necessary continuing education requirement in the trade for many years. And I mean that seriously!
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Regards: Klaus

...yes Sebastian. All corners, the bathtub area, and the entire shower have received an elephant skin.

It's great that Klaus doesn't hold back his knowledge here, we would have wished for such an expert during the construction phase! We had three of them(!), but unfortunately, none were convincing....

Yep, same for me - luckily without any expert reviewer