While they're notably playing a variant, this seems to be a fairly decent guide to the rules based on a cursory glance: https://www.pokernews.com/strategy/5-card-draw-rules-how-to-play-five-card-draw-...
And I used this as reference while I was initially programming the solver: https://www.cardplayer.com/rules-of-poker/hand-rankings
It's a distinct possibility that there's something not quite right going on with how the hand evaluator is deciding on hand quality, and I'm hoping to thoroughly investigate that when I start rewriting the code for the content patch in early December.