“Jojo said it’s free will versus Fate,” he said. “But I’m really just getting railroaded by two different GMs here."
"He unbound and unrolled the scroll, holding it up in front of him. It shimmered brightly. His fingertips tingled. There were words on the parchment, a poetic stanza. But he couldn’t read them at first. He was seeing something else.
No, not seeing. More like...detecting, or knowing. There wasn’t a word for this sense, but some little compartment in his mind opened up, and what was in there was as rich in information as vision or hearing. He understood some of the things behind the things he could see."
"He spoke, with a new understanding of how to intone the words of a spell. It was as different from plain speech as singing, but in a magical way"
Parson gained insight into how ALL magic works, not just Carnymancy when he looked at the spell. And from the two GMs comment I conclude that Parson is himself one of the GMs. Erfworld wants him to not swear, be a good little Chief Warlord that can't cast magic, etc. Parson self-limits (he conceives of himself as chief warlord, so he can't cast magic), but then during rare moments of clarity he overcomes these limitations (Like during the destruction of Ruthlessness he successfully swears and that's where he begins to conceive of himself as a free-willed actor as opposed to a mere pawn). Here in the magic casting scene we see Parson slowly beginning to conceive of himself as something other than Chief Warlord and then "POOF" suddenly he manifests the ability to understand how all magic works and the ability to cast quite proficiently despite never having cast before nor being taught how to do it properly.
I forget where Wanda said it, but Wanda pointed out that casting outside of discipline will always cost more juice and have a much greater chance of failure.
Parson is capable of Shocking people in ways that Shockamancers don't. This means he could satisfy the "Shock and Awe" requirement in a literal way without it needing to be "Parson has Shockamancy;" though I do think Parson will eventually be able to use Shockamancy and more.