Ah I think I just found my answer in the other Forum post here that Bill answered titled “Multiple attributes on Y axis with categorical X axis.” I guess the issue is we have categorical data on the x-axis, like the author of that post. The “Add Another Attribute” tutorial doesn’t seem to mention this limitation on not having categorical data on the x-axis by the way, so I might suggest you add it there.
Matt and I will look at your suggestions in that other post Bill for how to structure the data or graphs differently to accomplish what he’s after.