I am in the process of trying to update a copy the existing Zabbix monitoring template template_app_truenas_core_snmp.yaml to a corresponding scale version, and I would agree in calling removal of them a regression.
The missing truenas.zpool.size.total (.1.3.6.1.4.1.50536.1.1.1.1.4.{#SNMPINDEX}) and truenas.zpool.used (.1.3.6.1.4.1.50536.1.1.1.1.5.{#SNMPINDEX}) keys are really degrading the value of the template.