They couldn't get Android 13 in time? Seeing as it's already a major version behind, and 14 will be released in August 2023, you're really only getting another six months of software support (plus security fixes).
I'm not an Android dev but my understanding is that a lot of work has been put into making Android easier to upgrade major versions (eg, core functionality being split out into separate services). It doesn't look like that is translating into longer upgrade support, which is a shame. But I suppose that's why we're getting 5 years of security updates? (which is probably most important)