Well, when I talk about a fall, I don't mean the Fall of Man, but just the in-between-ish time and space between falling from a horse and hitting the ground. There is nothing especially Christian about that idea, in fact, liminal time and space were a significant pagan preoccupation. One can appease tutelary spirits within a house and gods and goddesses without, but whose got your back at the entrance? It requires the intrusion of the freakish, non-Olympian, Ianus/Janus ("Mr Doorway," from whom janitors get their name). Even the household gods tended to haunt liminal places like chimneys and hearths. The same apprehensions existed for thresholds (better carry that bride into the bedroom, you don't want problems now). And bridges, which are under the protection of neither the divinity of this bank nor that, nor of the river god beneath, were a particular source of anxiety (with trolls eventually coming to express the potential for trouble). To this day the Pope bears the pagan title of Pontiff/Pontifex Maximus, which is often translated as High Priest but which in fact means Great Bridgekeeper. Liminal time (including the transition to the month we're in now) was also presided over by Janus, but only after all sorts of social inversions and conniption fits about the Equinox involving other scary gods.
Many of these traditions have survived into Christian times in a quasi-pagan form, including but not limited to the nasty, gloomy, child-devouring Saturn becoming a jolly, generous, patron of children (a Saturnalian inversion if ever there was one). That gentleman is, in fact, a kind of fairy, dressed in the fur-trimmed red outfit of a leprechaun (right down to his red cap with the white ball at the end). My original point was that it is not surprising to find fairies in liminal time and space since they are liminal creatures in themselves (no winking), created illicitly by Christians as keepsakes of a lost paganism. It is therefore not to be wondered at (wink, wink) if, after slipping from one's horse, the Queen of Faeries swoops one up before the crash landing.
Your idea about the eventual landing as a return to normalcy also works in that scenario, or it does with Tam Lin in any case. (I've never read Ossian--didn't all that turn out to be a fake?). Tam Lin's return to the non-magical world required his mortal girlfriend to pull him off his fairy steed and protect him when he fell to the ground by wrapping him in her mantle. As I said, this probably represents the completion of his original fall. I don't think it was an affirmation of a link to the land, though. Tam Lin's earth was as full of fairies as the forests--hobs, cobs, cobalts, goblings, dvores, dwarves, you name it! Christianity or no Christianity, the earth was still an enchanted place.