Heey! Thanks a lot for playing the game! And it's so lovely to see someone picking up (and getting interested) in the terms used during brief dialogue lines!
I don't want to sound rude, but is it possible that perhaps you mistook "Dysarthria" for "Arthralgia?"
If my memory doesn't fail me, "Arthralgia" is the term for painful joints. Since "Algia" is the suffix for pain. Just like you take an analgesic for pain relief. "Dysarthria" is the inability to articulate. "Dys" is the prefix for Dysfunction/difficulty, and "Arhtria" means "to articulate." While "Aphasia" is the inability to understand speech or writing.
That particular moment sets the scene to show that the MC is knowledgeable. But if he were a health professional, he would've known he could never have said any of those disorders were ongoing since he would need to perform a few tests. That also shows that the MC either studied that at some point or had someone teach that to him (which is shown in the plot later on).
Sophia is the health professional (or was). SHE doesn't mistake the terms. But it's credible for the MC to be incorrect about medical disorders, terms, injuries, or conditions. And Sophia corrects him >:).
By the way, you might like the interactions between the characters in the future! (No spoilers)
And sorry about the long post; I get excited when talking about the game!
Cheers! And thank you for your service and for being on the front lines of care.