The idea of 'don't optimize if you don't have to' probably doesn't apply as much when developing a game for a 8-bit processor that runs at 4mhz with 8kb of working RAM, and when you are building a program which is inherently aiming to push the capabilities of the hardware with clever coding tricks (I mean the whole project is basically an exercise in optimization).
I think OP was saying they weren't sure if the original algorithm would be too slow to run under these conditions, and didn't have the ability to test it at the time, so they wrote it in a way which increased the chances of it running quickly considering the system limitations.