All things in development can take some time to fully implement. Zorin OS 17 brought a large amount of changes with the Gnome4+ Desktop, extensions and testing. Finding the right balance, along with the best backports meant more devotion to nuances.
A direct upgrade from Focal to Jammy requires switching repositories from Gnome 3.38 to Gnome 4+ and the backports set up.
Reasonably, what we can see from this is that the ZorinGroup released Zorin OS 17 to its users (many have been noting that they need the newer libraries for development or the later kernel for newer hardware) at the soonest moment that they possibly could.
If we need to wait a couple weeks for the Zorin Upgrader to be patched in, I would say it is well worth it.