The red light district is what visitors call Amsterdam's window quarters, De Wallen above all; for this house it is where people stay, never where it works.
In English the phrase is singular, as though there were only one. Amsterdam in fact has more than one area of red-lit windows: De Wallen in the old centre is the famous one, the Singelgebied a few streets from Dam Square is smaller and quieter, and a short stretch of the Ruysdaelkade in De Pijp faces the water on the edge of the museum quarter. When a visitor says the red light district, they nearly always mean the first.
Typed into a search bar, red light district massage usually comes from someone who has walked those streets, or is about to, and is wondering what exists beyond the windows. The answer is a different arrangement entirely. A window is somewhere you go, on its schedule, in view of the street. An outcall booking comes to you, on your schedule, in a room nobody else is looking into.
Plenty of visitors sleep within walking distance of De Wallen, drawn by the canals and the central location. For them the district is simply the neighbourhood outside the hotel door, loud until the bars empty and oddly peaceful afterwards. A booking from there runs on the same forty to sixty minutes as anywhere central, at the same rates, and the house keeps no premises in any of the three areas.
The comparison guide sets the two experiences side by side, and the De Wallen entry describes the quarter itself.