I speculate the level 3 spells are, at best, not 'ready for prime time'. Or even rehearsals. It also adds another layer of work; right now they can focus on dialogues, systems, new classes 'slotting in' properly, ect. Once that's stable and sorted, maybe we'll see another level (and all the abilities that need to be tested!) but I actually don't want a level 5 cap right now. Much prefer they iterate and bugfix what's already here.