We faced the same decision.
The electrician did run all the cables over the concrete ceiling, but the water pipes were nailed to the raw concrete. I tore off all the clamps again and slid the Katja sealing membrane underneath (the clamps come off quite well with a firm hit from a mitten hammer). Cheaper than Katja Sprint is the Björn Erika or Alujet sealing membrane. It’s the same system and also self-adhesive on the sides.
I then glued the Katja with the Katja Sprint Anschlussfix (a kind of bitumen compound) to the wall barrier membrane or with the Katja Sprint Anschlussstreifen.
The plasterers then told me that nowadays sealing membranes are very often no longer glued to the wall barrier membrane. They leave them standing up the wall like a kind of tub and then cut them off. If the sealing membranes are not glued, they no longer plaster all the way down and leave the lower 5 to 10 cm free. This way, with rising moisture, the plaster at the edges cannot draw moisture and flake off... instead, it diffuses out at the edges. Problems naturally arise if the floor is completely tiled... then moisture can no longer evaporate either, and the plaster will still get wet eventually... that’s why I decided to "tear out".
