There is no hard and fast rule that bathroom floor and wall tiles must be the same, but it is a common design choice for many reasons.
Using the same tiles on both the floor and walls can create a cohesive look and give the bathroom a more uniform and polished appearance.
Using different tiles on the floor and walls can create visual interest and add texture and depth to the space.
However, it can also create a disjointed or chaotic feel if the different tiles clash or don't complement each other.
Ultimately, the decision to use the same or different tiles on the bathroom floor and walls will depend on the overall style and design of the bathroom, as well as personal preference.
It's always a good idea to consult with a professional interior designer or contractor for their expert opinion and advice.