Since update 1.62 A dawn of renewal, the perceptor tab is hidden from members that do not have rights related to perceptors. However, they can still see the position of a perceptor that has just been placed.
For example, when a perceptor is placed, a message in the chat appears with the following info: "Perceptor [name] has been placed in [pos] by [character]". I was logged in with a character with no rights at all, and still saw this info.
I suggest to remove the [pos] info from the chat.