HAH! I KNEW IT!
I'm yet to get that banter (which I will, after I do a proper playthrough), but aside from other stuff we find throughout Trespasser, this strongly confirms what I suspected from the start - life evolved from spirits who have enough strength of personality to eventually gain enough of a physical form to become 'real' and find a foothold in the physical world.
(+ codexes in Shattered Library imply that some form of "unchanging world" - Earth, likely - exists, even if it was more intrinsically connected to the Fade before the Veil. Apparently Enavuris claim it as their domain and guard it jealously, banishing anyone they've found to be a threat outside its bounds ).
Elves (... and everyone else at some point?) were likely ones that were sort of beings that balanced and shifted between both worlds - some stronger and more defined, and some weaker and more impressionable/malleable. This would explain the existence of casts in elvhen society and also marry the concept of Creators (and other 'gods') being both powerful mages AND powerful spirits (at their core) at the very same time.
They have a physical shape, but it's not as relevant as the core of their being - it's relatively fluid and not necessarily bound fully to rules of immutable reality (this also explains why many old elvhen names seem to imply that its bearer is a personification of some emotion or concept. Or why Solas has a habit of using titles he thinks are appropriate for given people, rather than their 'earthly' names).
And the interesting thing about spirit!Cole is that at the end of his personal mission in base game, Solas tells everyone that at the basis of Cole's reversal to more 'spirity' being is him getting rid of his "self-imposed mortality".
What this also implies is - ironically - that while Cole began 'evolving' towards being a human, outwardly, he is likely the closest thing to what Solas considers "his people"!