I am looking at the Keynote v13.1 properties on Monterey 12.7.9 and it shows the minimum macOS and iOS collaboration versions are now 13.2. It would appear to me that Keynote is getting this information from the Mac App Store when it runs and updates its preference list accordingly.
This isn't Apple trying to hoodwink you into new hardware purchases as much as it is the introduction of new features in the current versions of Pages, Numbers, and Keynote that drive the current version collaboration requirement. These are internal decisions at the Apple product team level that are oblivious to how end users work.
Find a new means to collaborate (e.g. Word documents) instead of being tied to Pages application versions.