Tile is not waterproof
Neither is grout. Water passes through both. That is why Tile Council of North America details put a membrane behind the tile rather than trusting it. What sits behind the tile keeps water out of the structure. That means a continuous membrane, correctly lapped. It must seal at every corner, every change of plane and every penetration. A shower fails at its corners and its niche far more often than in the field.
Why shower waterproofing matters more on a slab
With no basement, a failed shower pan here does not drip somewhere visible. It goes into the slab and the adjoining walls. Then it announces itself months later, as a soft baseboard in the next room. By then the repair includes the floor.
Where shower waterproofing in Florida fails
Almost never in the middle of a wall. It fails at the curb, the corners, the niche and the drain flange. Those are the places where a membrane changes direction, or where someone cuts it. A shower that leaks is nearly always a detailing failure rather than a material one.
What we do
We inspect and photograph the waterproofing before any tile covers it, and you get those photographs. Otherwise it is the one part of a bathroom you simply have to trust. We would rather you did not have to.