Sealing bathroom for walk-in shower

Hello,
We are currently building a new house and today we received an offer from our builder for the partition wall of our walk-in shower. Originally planned was a level-access shower enclosure with a tray. Now the floor is tiled and the offer includes, in addition to the drywall, the sealing of ALL walls and the floor. According to the builder contact person, this is mandatory (I have requested this in writing).

However, I find it hard to imagine that I have to seal ALL walls. Personally, I think that sealing the bathroom floor and the shower enclosure is sufficient.

Can someone help me here?

Yes, the entire floor and shower. All walls is of course nonsense. Most tiles are not on the walls at all.

No is not enough. Simply put, imagine your bathroom as a tub about 10cm high. In the shower area, we make everything watertight, then usually go 30cm down from the shower wall towards the floor and lay our sealing tapes all around there, overlapping at least 15cm. I myself have a wheelchair-compliant shower measuring 2 by 2 meters. When my daughter showered for the first time without a partition, it was clear... Sealing all wall/floor joints is the right way. Since the topic of silicone will surely come up now... that is NOT a sealing joint, but a maintenance-related construction measure. Silicone is fundamentally never watertight... even if it might be at the beginning. P.S. especially in new buildings...

I counted that as part of the floor, of course you are right there. Sealing also has to be done at the skirting board height. Personally, I think it's nonsense, but that's how it is!

Our bathroom looks like this (see attachment). I would have assumed that only the areas marked with the x are sealed.

As the previous speakers already said, floor completely plus 15cm plinth. You can actually find it very quickly on the internet under image search: