Ardlings already had a built-in tie to the planes - they were designed with three "subrace" options to emphasize ties to LG, NG, and CG planes mirroring the new version of tiefling (perhaps the single most iconic Planescape race) and their options to emphasize ties to LE, NE, and CE planes.
The second pass revision to the Ardling didn't make them "more planar", it refocused them to be almost purely a representation of "animal person", with the ties to the Beastlands basically filling in as a default explanation for why they can represent any type of animal person rather than having separate species statblocks for each a la tabaxi, aarakocra, etc.
They went from representing a new type of broad-ranging celestial planetouched to being very specifically a unified anthropomorphic animal framework. That's not a problem, by any means, but the two fill different conceptual roles. Moreover, moving the ardling toward "animal person" ends up leaving the big "celestial planetouched" hole they had seemingly wanted the ardling to fill distinctly empty, so it's no longer serving the purpose it was initially created to serve.
I'm not averse to seeing the ardling return, but it still feels like there are some structural issues that need to be worked out, unless they're just ditching the "broad celestial planetouched" aspect entirely.