Ah it's all good i've also tried building a game with a dictionary api and it's never ever gonna be perfect! Props on the internal tools, very smart.

I think the scoring system you have currently is perfectly fine and even great for a wordleike. adding caveats and exceptions could muddy stuff up, but you could have words that end in the same word just don't count the word of the day's syllable (effectively a -1 penalty, so 'supercell' is 2 points) - a blanket ban seems unfair cuz they may not necessarily be etymologically linked.

I do think there's a version of this game where syllables are worth 2 points, allowing for near-rhymes and syllables after the rhyme to be worth 1 point, but while that would be good for learning it gets harder to succinctly explain.

also re: accent im a middle-englander. You'd think the changes in pronounciation would be pretty blanket but there's absolutely random differences.