PS + Start-WBBackup + Exchange 2019

I have a PS script that uses Windows Server backup to backup a Server 2019 running Exchange 2019.  I am finding that even though I am executing a full system HW independant backup, the exchange transaction logs are not being flushed after the backup executes.  If I run a backup manually, (mmc with Local backup snapin) the logs do get flushed.  Are there additional items I need to add to the policy.

# PURPOSE: Start-AssembleAndExecuteBackup - Assembles the required commands and values and executes the backup
function Start-AssembleAndExecuteBackup {
    try {
        $Policy = New-WBPolicy
        $BackupLocation = New-WBBackupTarget -NetworkPath "$NetworkFQTarget"
        
        Add-SeperatorLineToLog
        Add-UpdateLogWithSingleLine "L" "CREATED OBJECTS" ""
        Add-UpdateLogWithSingleLine "R" "Objects" "Policy, VolumeList, and Backup Target Location"
        
        Add-WBSystemState $Policy
        Add-WBBareMetalRecovery $Policy
        Add-WBBackupTarget -Policy $Policy -Target $BackupLocation
        Set-WBVssBackupOptions -Policy $Policy -VssCopyBackup
        
        Add-SeperatorLineToLog
        Add-UpdateLogWithSingleLine "L" "STARTING BACKUP" ""
        
        if ($str_Testing -eq "ON") {
            Add-UpdateLogWithSingleLine "R" "Backup Testing Mode" "ON (No backup performed)"
        } else {
            Add-UpdateLogWithSingleLine "R" "Email" "Email Notification Sent"
            Start-WBBackup -Policy $Policy -Verbose
        }
    } catch {
        Write-Error "An error occurred: $_"
        Add-UpdateLogWithSingleLine "E" "Backup Error" "$($_.Exception.Message)"
    }
}