Everything we see about pooka nature in the sourcebooks is a lie.
Think about the pooka from conventional myth for a second: often described as a terrifying shapeshifter that should be respected or feared. Now think about the real world association of animals and tricksters in human mythology; notice how many of them were antagonists. What's more likely? That pooka were born from dreams of childrens' laughter, or that they were born from the archetypes of feral creatures deceiving humans in order to lull them into a false sense of security? Even their abilities are unsettling: they are described as pathological liars who people implicitly trust regardless. Look at the different kithbooks' opinion section on pooka; no kith LIKES pooka exactly, but absolutely NONE of them consider them a threat. The greatest trick the devil ever played was convincing the world he didn't exist. Changelings are the larval form of The True Fae.
Not every Changeling wished to stay in the human world. Some, as they grew older, rejected their human nature entirely and embraced Bedlam because even being Mad was worse than fading away. They tried to retreat to the Dreaming wholly-and over time, twisted and warped the Dreaming into the realm of Arcadia. Alternatively, Changelings are True Fae cut off from Arcadia.
They remember Arcadia as a beautiful, wonderful place because it is filtered through the lens of the True Fae. Meeting Chronicles-esque Changelings would serve as a massive paradigm shift.