Better do it. The wall brick on the ceiling is above the ceiling position 10cm. The instructions do not say that it must be done at full height, but since it is a bathroom, especially for home use, the problem of humidity must be considered. Just like some bathrooms only have a height of 1.8m, and some have a full height. In the long run, making ceramic tiles is better than not protecting the wall. If a block wall is made. ...