I think "Good growing season" color should indeed be reserved for plants that exhibit something in their leaves that is unusual or interesting. As you said, zuzu, red, chartreuse, etc, is what this is intended for.
There are plants that are grown specifically for their foliage, and I wonder if that's what people are trying to say when they check this off? I'm thinking of tapioca, which has great foliage but is solid green. I believe it's worth noting that you'd grow it for foliage but I wouldn't say that tapioca has "good growing season color".
