Side-ring EXTRA · Parallel midras of niddah
Toras Kohanim (and the parallel structure already established for the zav in 15:04–06). Torah Temimah is silent on these three passukim because they transfer, almost verbatim, the midras framework already derived for the zav.
English: The same midras structure taught for the zav (“every bed on which the zav lies shall be impure …”) is applied to the niddah: anything she lies on in her niddah is impure, and anything she sits on is impure.
Structural parallel
These three passukim do not introduce a new category; they extend the zav’s midras (bed, seat, contact that requires laundering and immersion) to the niddah, so that her mishkav and moshav are avos hatumah in the same way.