The original quote has been lost in the Dataclysm, but the information exists in the form of a Farshtey Feed... Kinda.
BZPower is still migrating their servers, thusly the Farshtey Feeds cannot be read at the moment, however this is what the FF says:
• With respect to the Agori and Glatorian -- in one case, the title is a species name; in the other, it is not.
• The Glatorian are all of the same species.
• "Skrall" isn't properly the name of a tribe. It's a species name. We will encounter Skrall with individual names.
• Although Glatorian is a job name, not a species name, Greg does not see the Glatorian (those besides the Skrall) as being of separate species.
• Greg: "Skrall are not the same species as the other Glatorian are ... that's why they are stronger, faster than other Glatorian. While they do the job of Glatorian, they are not the same in the sense that they have no choice when it comes to fighting for their village. They are basically soldiers being sent to fight in the arena."
"6) How are Skrall, Bone Hunters, and Agori related to Glatorian? "
"6) Well, Skrall are close to them in terms of species. Bone hunters and Agori are not related to them, they're separate species. "