I think it's also not progressing the block size with score: IIRC the original came also begins spawning 8s and 16s once you get above your first 512 block. But I could be misremembering.
(This kind of feedback driven generation is one of the things I do find very impressive about LLMs. But it's currently more or less the only thing.)
I don't remember it doing progressive block sizing - I only vaguely remember being mildly annoyed by getting to 2048 taking >2x the effort it took to get to 1024, which itself took >2x the effort of getting to 512, etc. - a frustration which my version accurately replicates :).
(This kind of feedback driven generation is one of the things I do find very impressive about LLMs. But it's currently more or less the only thing.)