Even those who are devoted to other deities, who worship, who honour, them, joined with faith, attended by a believing turn of mind: even they worship Me alone, O son of Kuntī, but not in the prescribed way. The 'not-prescribed' is ignorance; they worship with that ignorance going before. Why do they worship not in the prescribed way? It is told. Because.

Even those who are devotees of other deities, those who, devotees of the deities Indra and the rest, settled in the threefold knowledge alone, joined with faith, sacrifice to Indra and the rest, they too, by the principle stated before, since all things, being My body, have Me for their self, and since the words 'Indra' and the rest denote Me, in truth sacrifice to Me alone; but they sacrifice not in the prescribed way. The texts of the Vedanta enjoin the worshippedness of the deities, Indra and the rest, in the rites, by such words as 'where the four priests come to a meeting with the gods', but they do not sacrifice in the way preceded by that. For the host of Vedanta-texts, enjoining the worshippedness of Indra and the rest who abide as the body of the supreme Person, enjoins the direct worshippedness of the supreme Person alone who is their self. The four priests, carrying out the rites, the fire-oblation, the new-moon and full-moon, and the rest, come to a meeting through the gods, Indra and the rest, who are His body, only where the supreme Self abides as their self; that is, since these rites, the worships of the gods Indra and the rest, have Me for their object, they come to a meeting with Me. This is the meaning. Therefore the men of the threefold knowledge do not know that these rites are worships of the supreme Person whose body is Indra and the rest, and that He alone is the one to be worshipped; and they become partakers of bounded fruit and of a perishing nature. The Lord says this.

This is a brief sub-gloss. For a fuller reading of this verse, see Madhusūdana, Śaṅkara, or Rāmānuja above.

Then 'I am the rite' (9.16) and the rest would be untrue; to that Krishna says, 'even those who'.