If I remember correctly, the issue is this:
When a thaumaturge or a conjurer uses aether, they draw it from the source, and then they put it back somewhere. A Thaumaturge might expel it into the environment where someone or something can reabsorb it later. A Conjurer might just let it disperse into the environment in the same way.
On the other hand, when a White Mage or a Black Mage uses aether, in order for the spells they use to have the effects that they have, that aether dissipates entirely instead of returning to the environment. In other words, when they cast their spells, they contribute to the "magical heat-death" of the universe.
When a thaumaturge or a conjurer uses aether, they draw it from the source, and then they put it back somewhere. A Thaumaturge might expel it into the environment where someone or something can reabsorb it later. A Conjurer might just let it disperse into the environment in the same way.
On the other hand, when a White Mage or a Black Mage uses aether, in order for the spells they use to have the effects that they have, that aether dissipates entirely instead of returning to the environment. In other words, when they cast their spells, they contribute to the "magical heat-death" of the universe.
