I don't know why they bothered bringing up that the doggies couldn't be sensed if they weren't going to do anything with it.
They kind of did. It's the only reason they were able to box in Goku the way they did. I do think it was a weird aspect they didn't do enough with though.
Could say the same thing about 100x Taiyoken...
Now that really bugged me. It would've made more sense if they blinded Majora with it and then he switched to scent as a counter, instead of just making the move worthless right off the bat. Majora's eyes are even open in the intro!