Author here - Thanks! You are absolutely correct there are several state machines (vga, sdram controler, framebuffer, texturing, divider, renderer, etc) and each with an active state index. The renderer is the biggest one with 69 states.

I agree the state index can be seen as an instruction counter, albeit into very specialized instructions: there are no two same instructions in a given module, each is uniquely implementing a precise subpart of the algorithm. Also the states decide the flow and select the next state, there is no list of instructions you could program or re-arrange. So I wanted to capture this idea that the algorithm is completely embedded into the circuit itself, which is not capable of doing anything else.

There is definitely a very interesting trade-off between a general instruction set and an extremely specialized state machine like here - combining both seems promising?