Your understanding is correct. Different millers and flour vendors use different terminology to characterize the protein and gluten contents of their flours. One miller's bread flour can have a protein content that is close to someone else's high-gluten flour. The King Arthur brands of flours tend to have higher protein contents than competing brands--pretty much across the line--so that in itself can add to the confusion. On this forum, the practice has been to distinguish between high-gluten and bread flours, if only to minimize confusion. But you are correct that bread flour can be considered as a high-gluten flour, and, as I mentioned, some millers refer to their bread flours as such. When in doubt, I usually try to look at the specs (if available) for the flour in question. At around 14% protein (it's 14.2% for the KASL), I know it is "high-gluten" for sure.