ToME: the Tales of Maj'Eyal

If you have an addon that adds talent trees to Adventurers, does this mean rare NPCs can also get them?

Anyone know?

Yes, they do get them

I don't think this is necessarily true. You can add trees to adventurers by allowing npcs to have them, but you can also add them to the adventurer class manually, or remove the restriction that prevents adventurers from getting trees banned on npcs.

Which method does adventurers_unlocked use?

I would guess the first, since that's the simplest way to just let adventurers use any talents other classes can, but I haven't actually looked at the code