Without knowing too much about the context, it probably would have been possible to keep the structure where every shape is structurally independent from other

Without knowing too much about the context, it probably would have been possible to keep the structure where every shape is structurally independent from other shapes, but where calculations are abstracted away in pure functions that are just being called by the shapes. That keeps the maths in one place (and you can always add more calculation functions later if needed), but it doesn't entangle different shapes with each other needlessly.