The alarm definition includes a trigger to set the alarm back to normal when Pending storage recommendations were applied.
Under Fully Automated mode, the alarm is triggered and a recommendation is applied, but the alarm is not set back to normal and only can be cleared manually.
VMware vCenter Server 8.x
VMware vCenter Server 7.x
This behaviour was changed from vSphere 7.x and above where the alarms are not cleared automatically by design.
Engineering is aware of the issue and will implement a fix in a future release.