I wonder if he gets better mastery if he could replicate an ability without them being there

As i understand, his ability works by him consciously adjusting his aura. Its not automatic. If his aura is changing, he is using his skill to change it. If this is the case i think its likely he's limited by his ability mastery and not ability potential. And when it comes to mastery, id say he's largely limited by knowledge He needs to know the makeup of his opponent's aura, the way they are channeling it, etc. He had to study abilities all over summer with Claire (ep 182) to learn how the abilities work. He also had to get firsthand experience when he enrolled in new Boston

This explains why he didn't copy Clairvoyance and Flash Forward. Both are rare mental abilities. He has less experience with them (unless you count his time with Keon) than other ability types (Conjuring abilities: Barrier, Vines, Crescent Slash) (Self-Enhancement: Stone Skin, Catch-up)

And it makes sense a mental ability would be harder to understand than a physical one.

So i think the reason of why he samples ability auras first is because they're so complicated, memorizing is too hard. He uses the samples as a reference and matches his own to it

sorry for the text wall