The quarterly cycle applies to regular FreeBSD packages and Nextcloud is available in flavors PHP 8.0, 8.1, 8.2 and 8.3:
Nextcloud Hub is an online collaboration platform that provides groupware capabilities by default, and can be extended with additional apps.
www.freshports.org
What must be updated to get a newer version in your plugin is this:
Official iXSystems iocage plugins for FreeNAS and TrueOS - freenas/iocage-ix-plugins
github.com
This is completely independent of any FreeBSD package maintenance or Nextcloud releases and poorly maintained. Which is why everybody recommends to just drop it and perform a manual or scripted installation.
Understood? On top of the regularly updated maintained and reliable FreeBSD operating system and package infrastructure somebody created a "one click TrueNAS plugin". All the FreeBSD software is perfectly up to date. But that person plain neglects updating the plugin to follow FreeBSD's lead. Nothing the FreeBSD project can do about that nor a fundamental flaw of jails. Just an abandoned "plugin".