I wouldn’t point a 7 year old to this file, but the code is the source of truth. I do think that section is comprehensible to a layperson. I appreciate you taking a go at it!
Under "japanese" there is this line:
defaults.score_territory_in_seki = false;
So OGS tries to handle it (it’s not always successful AFAIK)
There are other rules like “bent four in the corner” or “triple ko” which aren’t respected. But I think this is more a topic for Odd Cases 🤔 in the Japanese Rules