Why did Buddha praise the vedic Agnihotra as the foremost sacrifice?

Why Buddha praises the vedic Agnihotra as the foremost sacrifice and the Gayatri mantra as the foremost meter in the Pali Canon?

aggihuttamukhā yaññā sāvittī chandaso mukham.
Sacrifices have the agnihotra as foremost; of meter the foremost is the Sāvitrī

"On the Buddha's Use of Some Brahmanical Motifs in Pali Texts"

Above quoted text is from M.N. Sela-Sutta, that buddha taught to selabrahmaṇa:

aggihuttamukhā yaññā sāvittī chandaso mukham.
Sacrifices have the agnihotra as foremost; of meter the foremost is the Sāvitrī

So, buddha didn't taught veda. Buddha just use selabrahmaṇa's knowledge, veda, to teach him the last line:

puññaṃ ākaṅkhamānānaṃ, saṅgho ve yajataṃ mukha’’nti
Saṅgha is the best foremost of wholesome-mind developers.

This last line is the real buddha's teaching. Your quoted line, veda, was used by buddha just as alike as a tool to make selabrahmmaṇa understand the last line.

How can you taught new language for a foreigners? You use their knew-language to teach them new language, right? That is what buddha did.