I could see the confusion but, how I see it absolute intelligent being/person can understand and learn any concept, matter, or information present to them immediately. This would mean they could learn everything in the universe or beyond given enough time. This would mean they could reach a sort of nigh-omniscience, but the key difference is someone with nigh-omniscience would know the information rather than having to learn it. While achieving Omniscience would be impossible for this power. To put it simply absolute intelligence is what nigh-omniscience is minus having to go through vast amounts of information while Omniscience isn't limited and wouldn't have to learn information it would already know everything. Hope this helps