Tiler DIN slanted tile - does it have to be like this?

I don't understand the tiler. Instead of removing that one tile and re-laying it with a bit more adhesive, he tells such nonsense?

If you want the slope towards the bathtub (I would consider that professional), then arrange it that way. Whether the tiler does it as a goodwill gesture, you'll see.

Put the spirit level in that corner. So you can see if the bathtub also has a slope inward.

Thanks first of all for the answer. It is important to know that there is no regulation as he claims.

In my opinion, it is not professional if at least the slope of the bathtub is not created. That can also be horizontal. But towards the wall is wrong. Water will always remain there if any gets there. Show us a picture with the tiles.