I'm not going to comment on the rest of it, but as to the quoted sentence, I agree. Just hearing her voice again doesn't tell us anything. I doubt she's suddenly in a much better condition than when we left her, just because we beat up a few primals and didn't rely on her for a month or two.
The scene where you finally hear he again felt really bittersweet to me, in the "yay, we succeeded, mom's back from the hospital! But oh no, mom still has stage 4 cancer and she's come home to die" type way.