The point is that it's still high and stagnating. And the living wage calculation is using a CPI adjusted fixed level, so inflation that's heavy on critical sectors for lower income people (housing, fuel, groceries) will show up less than the real damage it's causing.

They set it up this way because TRU is a conservative measure designed to stand up to criticism. The true under-living-wage rate is probably even higher but that would depend on stronger assumptions that are easier to attack.