There's a couple of ways to think about this. It's all about alignment, as I'm sure you know. First, your rear pulley is as wide as the belt. It 'floats' on the front pulley, as it is much wider than the belt. The relationship between the two is dynamic, and is controlled by how you align the rear wheel.
Some go for 'perfect' wheel alignment and don't care where the belt winds up, and it may rub a bit on one side of the pulley or the other.
Others go for belt alignment. You can lift the bike, spin the wheel, and hand force the belt to the other side of the rear pulley. Keep spinning the wheel, and if the belt just makes its way back to the other side, where it's been rubbing, I do this...
I go for as good a wheel alignment as I can get it. I use the straightened metal coat hanger in the hole of the hollow swingarm pivot bolt to the center of the rear axle bolt. If that can make my belt center on the pulley, I'm pleased with that. But...
If my belt won't center, I'll start manipulating the right alignment adjuster a bit of a turn at a time(as I've already got belt tension where I want it), while turning the wheel, and watching the belt move in the pulley. If, with just the slightest adjuster bolt turning, I can center the belt... I tighten it all down there.
Like I opened with, others go for 'best' wheel alignment, I go for 'best' belt in the rear pulley centering. Is one more important than the other? I can't tell that my wheel's are out when riding, by concentrating on belt alignment.