Niches in shower walls have every face lined with a water-resistant substrate, their internal linings separated from linings on the other side of the wall, waterproofed on every surface with fillets or bond breakers to suit the membrane (4.10), and their base falls at 1:100 or steeper toward the shower.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.