How to find if Volume Efficiency has been enabled using PowerShell Toolkit

I am trying to find all volumes on a cluster that do not have efficiencies enabled, but can't seem to get my syntax correct.  What am I missing?

Running the code below returns all the volumes that DO have SIS enabled on them:

$Vols = Get-NcVol
$Vols | Get-NcSis | Where-Object {($_.State)}

But, I can't seem to get it to return the volumes that do not have any SIS settings at all.  I've tried each of the following with the assumption that the property doesn't exist for any volumes that do not have SIS enabled:

$Vols | Get-NcSis | Where-Object {(!$_.State)}
$Vols | Get-NcSis | Where-Object {($_.State -eq $NULL)}
$Vols | Get-NcSis | Where-Object {($_.State -notcontains $NULL)}

All of them return nothing, even though there is at least one volume that does not have SIS enabled.

This is OnTap 9.5P3 and PSTK 4.7.

Thanks for any suggestions!