I had a pic somewhere here that showed the Energex CA plant filling the FSU bags. I highly doubt they are using a different blend of fiber for the FSU and most likely are using the same fiber as the Energex CA.
From a rep I chatted with, The reason they are saying a higher amount of softwood in their blend is due to its what they get from the saw mills they buy from. Most of the CA mills are cutting SPF for 2x lumber. The hardwood they get isn't as abundent as it is down here. PA mill is mostly hardwoods, But they do except a little bit of SPF and the amount varies. So they don't even specify what the blend is.
From a rep I chatted with, The reason they are saying a higher amount of softwood in their blend is due to its what they get from the saw mills they buy from. Most of the CA mills are cutting SPF for 2x lumber. The hardwood they get isn't as abundent as it is down here. PA mill is mostly hardwoods, But they do except a little bit of SPF and the amount varies. So they don't even specify what the blend is.