A bit late but:
Well, the rule 1.7 clearly address pre-pubescent characters, so you're right.
As for the rule 9.1, it probably mention teens because it specifically target realistic depictions. While it's relatively easy to see that Daz renders or 2D drawing aren't real characters, and therefore that it fall under an artistic, or none realistic, exception. What wouldn't be as easy with AI generated images that want to be realistic.
I'm sure that, in top of not wanting p*d*shit addict to starts coming here, the staff don't want to have to explain to a judge that "those are AI generated persons, not real ones".
Westy got prosecuted, and jailed, for his game (and two cases of stalking), while it was bad Daz renders. No need to have superpowers to know that times would be really hard for the staff if there were AI generated realistic teens involved in sexual activities available here.
Even if they win the case at the end, it would be a long and expensive process, and it would expose the forum for its piracy activities. Both the staff and users would suffer from this, all this for a bunch of guys who want to fap to naked 16yo or less girls/boys that looks like real persons.