So, for what I understand, they keep playing the songs half step down live, right?

Even with rollercoaster being played a full step down from the standard tune live, it's still half step down from the album version, isn't it?

I guess what you're trying to say it's that playing a full step down doesn't sound bad, so they can do it with the old songs. But I think what would sound bad wouldn't be playing with that tuning, just the fact of playing a full step down from the album version, regardless of which tuning is used.