Pool cover tracks that is...
The track sits in a groove in the wall and overlaps the top of the waterline tile. The remaining wall above will be filled and tiled down to a finished edge with the top of the track.
A closer look at the track in the raised bond beam and also of the deck plates that go over the pool cover box. The coping will be set in mud on top of those plates and will finish flush with the deck.
Here's a view of the track and deckplates still exposed on the north side of the pool. The coping will cantilever over that track obscuring it from view when finished.