I don't see Threads when I try to block it as an instance. Why?

Went to the block page in Settings and typed "threads" into the instance field. Threads.net didn't show up. Is this because they are already blocked by SDF? Or are they still getting my content? I already had a Threads user reply to one of my comments maybe a month ago. I decided to wait and see how I felt about it and I'm certain: I don't want my posts reaching them. Thanks in advance.