I’m not sure that you do. Pretending to not understand something you then say that you did understand is not sarcasm. It’s more like feigned ignorance. And while I guess that can be used to point out that something is unclear, in this case the thing was clear, so the ‘joke’ didn’t really land

If you were joking, then you figured out what they meant. If you figured out what they meant, then everyone else can too. Their wording was fine and clear within the surrounding context

God I hope you meant to type ‘threat’

“swallow the completion” really sounds like a fellatio joke…