There's still merit to the mentorship theory imo, aside from the numbered lists suggesting each teacher's assignments, the close ties between each mentor-mentee could also be a way of strengthening the teacher's faction. The only pearling to have occurred recently seems to be Julia's (plus Trent), held under Cho's supervision. If her group has a monopoly on the proceedings, the latest recruits could all be subservient to Cho (possibly exposing another layer to Cho and Macky's argument over who gets to handle Dilan after Emily's dorm fiasco).
You're probably right about Dilan not being able to get pearled, too; bodily reconstitution is one of the things a Pearl seems to experience, and our boy has proven he's able to regenerate to his natural, whole state no matter the injury. Gatastate may try it anyway, so I'm interested in whether Nalid/Katja would do anything about Niht's influence or just roll over and let a repeat of Akuaki + Verl happen.
Also my guy, what a wicked pfp you've got
Idk about artstyle, but based off the facts regarding the missing sister, it would seem Julia is who Caroline is looking for. Going into speculation territory, Julia might be the demi with dormant magical blood described by Allan in one of his reports, which could be related to how Caroline came by her lipstick.
Differences seem to end at Walter's death, the only notable update is the name of the Fragment hidden by Katja in Verl's event (Fragment of Warmth/Cold/Self).