Mashiv Haruach is not a tefilla for rain. We are “remembering” (or maybe mentioning is a better translation) HKBH’s power to bring wind and rain. See the “title” to SA: Siman KUF YUD DALED:
Just to add to ubiquitin’s answer, The mishnah and gemara in the beginning of Taanis discuss this, and we pasken to only be mazkir at the time we are shoel, and not even at the beginning of Succos, despite the fact that that’s when the judgement on rain takes place, because rain on Succos is a siman klalah.
That the fact that it is merely “remembering” (mentioning is indeed a better term) should allow us to say it even when we don’t want rain (we are praising Hashem for bringing rain at its proper time) is R’ Eliezer’s sevara, but we don’t pasken like him.