Is it mandatory to have an octagonal angle for the toilet waterproof base?

No. Make sure that the construction site is clean and dry before the waterproof construction of the toilet, and the waterproof coating should be painted without omission, firmly combined with the base, without cracks, bubbles and falling off. The practices and specifications of various waterproof companies are different, so the internal angle of toilet waterproof base is not mandatory. The base at the corner of Yin and Yang of the waterproof layer should be made into a 45 fillet or a splay according to the requirements, and the splay foot is 50mm long.