This is an odd thing to be told. He needn't bother telling them at all, but that is what's happening, and so they give it due attention.

They are not a worthy subject to study. They were not part of Hallownest but for their part through failure. Perhaps, if he wishes to study its ruination--

The teacup trembles and lowers slightly, and their gaze along with it.

--he does not.

(Not now.)

As they must, the Hollow Knight accepts it.