From my understanding, we're still searching for empty space? We just have an easily computable sequence of spots to check. E.g., if our stride is 7 blocks, then instead of going linearly with a stateful search, we can easily compute where we check. It's hard to pull this apart from the README. The README looks a bit LLM generated (clued in by OP's comment as well), which contributes to the difficulty versus a more thoughtful writeup. Interesting idea, it's just hard to tell exactly what's going on.
This is on GitHub's official account. For some reason GitHub is deploying this on GitHub pages without a different domain?