I'm guessing it's confused by the peer to peer system.
PeerTube allows small servers to reach big audiences by using p2p. This means if you're watching and lots of other people are watching the same video, you pass bits of the video to each other to take the strain off the server.
In theory you might be able to see the IP address of somemone who is watching it at the same time as you, but in practice this is kind of tricky and you're not going to know who they are anyway.