I'm not sure that meets the criteria for a "cycle of the stars" since it's a planetary change, but I guess for Hipparchus it probably did look like a celestial change. It definitely doesn't match the claim that "we do not try to ask HOW civilizations past could have been aware", though. We know exactly how Hipparchus recognized this. Nonetheless, this is a reasonable response to my question.

Noting a long-term cycle of equinox precession is impressive but also not terribly surprising. If you can note the change, you can reasonably assume it's cyclical (because the alternative is that it's going to suddenly stop moving at some point in the future).