I thought the loop was the aerial that went around the room and the receiver was built into some models of hearing aid. a la What is a hearing loop? - Hearing Link
I was leafing through a pamphlet at the audiologist’s office a few months ago. This pamphlet was specifically focused on hearing assistance in churches. The author’s view was that telecoil was headed the way of the dodo. I doubt we’ll see many new buildings wired up for it.