Why can't you see it is twofold? Both were at issue in the book, and you seem to deny that, and that they were called to leave the elementary as I have been stressing al along, in Hebrews, and Galatians..
My point stands. You want to argue about what the elementary is, while the word needs no definition, t he gildren, or as said below, the INFANT.
Jamieson-Fausset-Brown Bible Commentary
14. strong meat—"solid food."
them … of full age—literally, "perfect": akin to "perfection" (Heb 6:1).
by reason of use—Greek, "habit."
senses—organs of sense.
exercised—similarly connected with "righteousness" in Heb 12:11.
to discern both good and evil—as a child
no longer an infant (Isa 7:16): so able to distinguish between sound and unsound doctrine. The mere child puts into its mouth things hurtful and things nutritious, without discrimination: but not so the adult. Paul again alludes to their tendency not to discriminate, but to be carried about by strange doctrines, in Heb 13:9.
Bottom line, legalsim is elemental, and other things can be too. you are trying to isolate the text, from the whole of the context of the whole of the book.
How am i wrong about stoicheion?