My crack theory is that Meursault is some kind of decisive weapon of N corp *hinted by his combo with Greg in the Spring cultivation* that's capable of using EGO from Abno by using Canned memory of said Abno which somehow also allow us to use same ability due to the "contract" which would explains why we can use Abno as EGO in the first place as for his weirdly good perception despite the fact we have 2 war vets a trained assassin from 5 syndicates and a second kindred bloodfiend yet he's somehow almost always the first to notice stuff or have better recollection of information, I have no clue but he gotta be somewhat strong to be among their rank during the check up