Yeah, that's expected. Mute lists are saved to the author's outbox relays like any other note and most clients don't encrypt their contents, so anyone can readily see who is on them.
Discussion
No no. Not the contents. The content section.
Really? From the looks of it, the content section of nostr:nprofile1qqswum4p82uluhz2dr40nvdrflspffntgqghc58w9fs57nx6jkdkuaqd5rvcc's mute list is encrypted.
It looks encrypted if I view it in Damus, but if I open the note on nostrapp.link it shows around 200 muted npubs. I think it just comes down to how each specific client is coded to read or display the data.
So, it looks like there are 196 npubs on your mute list that are not encrypted at all, visible to anyone who cares to look. Then there is a chunk of encrypted information in the "content" tag that likely includes other npubs none of us can see, but you alone would be able to see if you go to your mute list in your settings on Amethyst or Coracle. Damus will not show these encrypted entries on your mute list. Most clients don't.