[Sawrock]

It's not out-of-character information to notice someone is affected less by healing magic than others being healed as well.

If we were in a club, and all club members had their left arms broken (for the tax benefit in this hypothetical county), and someone broke into our club, cast healing on all of us, and all of our arms were healed except yours, I'd be wondering why. If there was a in-universe reason for that (for example, the knowledge that homunculi heal less than others do) then it wouldn't be a jump in logic to assume that's why it happened.

I really can't see how it's metagaming for people to see what is happening with their IC eyes infront of them and make assumptions based off of their in-universe knowledge, especially when there can only be so many situations of what could cause said lack of healing.