I think Forever Young got beat by Boombayah and Really by AIIYL (and See U Later was eliminated in a 3-way b-side battle). And this was a couple months after the release, so I thought Forever Young might at least stand a chance. I think it was more that the title tracks just had more power.
And yeah, I know people listen mostly to titles (that's what I do with most groups), and that's part of the reason why I'm still surprised the b-sides did so well in the Red Velvet tournament. And it's also the reason why I ONLY did it with Twice, BP, and RV, because I figured they were big enough for many people to be aware of some of the more popular b-sides.
Here's that RV Tournament bracket btw: