Lyxen
Great Old One
One could make the argument that phlogiston is largely derivative to the Astral, and should be discarded. I do not interpreted this line as specifically tied to the example of "Slut Street" and other awful naming.
The phlogiston has nothing to do with the Astral apart from being a "transition plane", just as the Astral has nothing to do with the Ethereal. The description is completely different and so are the mechanics, as the Astral is really a spiritual plane, contrary to the Ethereal and phlogiston, which are very material (for the ethereal, not in itself but in the fact that it connects to the elemental planes that provide the matter of the prime). Of course, you can try to mix things for simplicity, but you also decrease the richness of the setting. What the heck, why do you need other planes for, just call them planets.