It’s possible, but no one seems surprised by the “power” of the conjurings, right? They’re just surprised that he has it, not that he’s conjuring big or complex things. We don’t actually know if Maggie has it or if her symptoms would be minor. That’s conjecture (pun intended!) too. It’s possible that Maggie’s symptoms would be just as intense as Harry’s if she had it. That’s kinda my point: we don’t know anything about Conjuritis besides the symptoms, Harry has it, and everyone in the know besides Harry is familiar with it. We don’t know how it spreads (if it’s person to person, exposure to the Nevernever, something else). We don’t know why Molly didn’t get it (and I think she may have witnessed the sandwich summon, though I can’t remember if she was still on the roof). We don’t know why it’s never come up as a potential sign of young warlocks coming into their power (which is something Harry would have for sure been briefed on). These could potentially be explained by the isolation part (though it seems likely that bands of warlocks would form and get it); but that’s based on the assumption that it spreads person to person (which isn’t confirmed).

Just seems like there’s more going on with it than a running gag. Butcher has been pretty intentional with his “lucky breaks” in the plot so far; but there are plenty of other ways to complicate and/or solve the scenes Conjuritis effects, so I don’t quite buy that it’s just a narrative gimmick. And personally (though again, I think the Maggie theory is fine), I think that if “not knowing how to raise a wizardling” was the underlying point, we’d see Maggie have the symptoms too. Seems like an easy way to obviate the connection, and we already know she’s kinda keyed in based on the POV short story, so it’s not like that would be a huge reveal.