Rav Sorotzkin's Chiddush In The Beracha Of Sefirah

In this sefer of Rav Yitzchak Sorotzkin he wants to suggest that the beracha of sefiras ha'omer isn't a classic birchat hamitzvot, rather its part of the mitzvah of sefirah.  Now, I find this to be crazy, how can a birchas hamitzvah which is merely Rabbinic be part of the mitzvah?  Where do we ever have such a thing?  The most similar thing would be regarding the birchos of shema where some Rishonim say the מצוה כתיקונה can only be fulfilled together with the berachos.  However ,that is because the berachos of shema aren't classical birchos hamitzvah, they are meant to put one in the proper state of mind to accept עול מלכות שמים but we never find such a concept by a run-of-the-mill birchas hamitvot; why would sefirah be any different.  I believe many of the points he raises can be deflected by noting the nusach the Rishonim had in counting sefirah.  We (ashkenaz) say היום יום,  the counting is distinct from the beracha.  However, they said the breacha and concluded the beracha שהיום יום וכו, meaning the counting is part of the text of the beracha.    It's not that the beracha is attached to the sefirah but because of the nusach, the sefirah is part of the beracha and that's why dinim of the sefirah get carried over to the beracha, for they are inseparable.  In the Ravyah it is explicit with the text שהיום יום וכו.  Regarding the Machzor Vitri that brings the Rebbe of Rashi counted earlier and then repeated the count with a beracha, the poskim all ask how he repeat it with a beracha if he already fulfilled the mitzvah?  This law is cited in Shulchan Aruch (489:3) and various answers are given by the commentators.  There is no reason to extrapolate from here crazy chiddushim.