The answer to this question can be found towards the start of this chapter (Chapter 23). By my count, it starts around five paragraphs into the chapter. I guess that is where I would say the "proof" is.
What the narrator says is that Mr. and Mrs. Pocket are not really the ones with the power in their home. You would think that they would be because it is their house, but instead, it is actually the servants who seem to have the power. The narrator says that the servants let the Pockets have lots of nice stuff, but that it still appears that the servants keep all the best stuff for themselves.