The reason why word size is so confusing is that we started sharing architectures (partially or fully) across multiple CPU designs, baking in the word size of w

The reason why word size is so confusing is that we started sharing architectures (partially or fully) across multiple CPU designs, baking in the word size of whatever CPU design was first. And even Architectural word size has fallen out of modern use. CPU word size for individual CPU designs much easier to define. It's not really the bus size, though it was strongly correlated until caches and bus-multipliers became a thing (For example, the PowerPC 601 has 32bit words (and 32bit registers) despite having a 64bit bus) Word size is the native operation size. The size of integer you should use in your code for the best performance. Which is why the 68000 has a 16bit word size despite having 32bit registers, because instructions for 32bit operations took a few cycles longer.