Big deal, so they’ll do Chalitza instead of Yibum?
DY, so you are saying Mochel half instead of Mochel the whole.
PAA, you are right. So that Pshat is out the window. We are left with 1- The Chashash is about someone else. 2- The brother is Mochel (Not optimal. Okimta.) and 3- Yerusha of his mother. (Also problematic because the Halacha is probably that he rightfully is her Yoresh).
The first is true anyhow. This is how all Chashashos work: we don’t want people to confuse the Halacha. Yevamos is full of this.