If…..

[Katish]

The lore is not concrete, it can be changed. They could make it so that Pixies (or all Fae on the first) are the original form of the "Fairy". When they die (again?) or shed living material, that material has a chance to become an aetherical being. These beings could then be what we know to be as the scholar's fairy. Since we only have the First as an example, we can assume that the Source also had a "King of the Fairies" and since the control/image of the king is so ingrained into the fae, they take that image when reconstructed, or at least something in a similar form (the fairy), similar to how primals are based on the twelve and have those distinctions but aren't exact. The higher concentration of aether the closer to the original (which explains how Feo can make smaller versions of herself). That way, we could have it fit in with the lore on how we could possibly get Titania/Feo UI and it would explain as to what the Fae on our world are. They could also take it a step further by having the scholars of old not even know what the origin of the fairies were, but by chance found them in the state they are now. The fae on our world could have been wiped out due to several possibilities allowing only the aether to remain, the aether then constructing some of those fae (fae essences(?)) into fairies.

Etymology from the fandom for Fairy:
A fairy is a type of mythical being or legendary creature, a form of spirit, often described as metaphysical, supernatural, or preternatural.

Aether on death:
Aether is released from the body upon death and it disappears from the physical realm to mingle back into the aetherical sea from which all life begins. Only so much of it can cross over at a time, and any excess remains to form a glowing mist, crystals, or even ghostly apparitions. As aether is akin to soul energy, more violent and dramatic deaths tend to yield more excess aether.

The form would construct from the spirit (or matter) of the fae and become a fairy, and since fairies gives off that apparition-feeling, it fits.