"There is some precedence for beast bonding, as my husband's people do, though not so deeply, but it is not what you describe. Do you truly purport to be able to change a beasts nature?" Jaromila asked.
Huh, is the Empire's spirit binding practices really so special? Does the Cloud Tribes' beast soul-merging not provide the bonded beast with similar human flexibility as the Imperial methods?
Well, I suppose that might be a factor in the Cloud Tribes' current troubles: they are unable to change their beast partners' Ways to account for the Empire's habitat destruction and invasion, leading to the slow extinction of all human-competition apex predators like IRL, winnowing the number of prospective beast partners talented enough to make it to their "Sky" Realm (equivalent to the Empire's Eighth Realm).
(I wonder if any Tribesperson will give up easy flight, and bond with a city-compatible beast, like dogs? We know, from the spirit beast advancement sidestory, that dogs are an exception to the general rule that spirit beasts need to run wild — to have a region to rule, to follow Zhengui's phrasing — to advance in their cultivation.
Unlikely, with the current Empire-Cloud Tribes relations, to see any in Empire-controlled areas, but maybe later? Possibly in the White Sky Confederation's lands?)
"Spirits do not change. That is the province of the human," the Voice said.
"Sometimes a spirit splinters and is remade, but this is not change," Jaromila said, sounding troubled. "It is rebirth, the creation of a spirit with a new mantle.
This sounds like their spirits don't advance in cultivation, that they're all frozen in stasis. Any advancement thus would have to be in the direction of "the same, but more so," like generations of snowfall packing ever more ice upon a glacier.
I suppose, here, the spirit-human relationship is all only unidirectional—the spirit teaches the human, and learns nothing in return. To map it onto Zeqing, placing spirits in the role of objects of reverence and veneration, imposing a stasis on their relations. It would require a different viewpoint — that spirits are things to be manipulated and used, to take the Imperial perspective — for a spirit to adapt and change their Way.
...Perhaps the Hill Tribe methodology of spirit interaction would also be helpful here — the Trickster King changed the nature of the King of Wolves into the King of Hounds, after all, and made dogs as humans' best friends.