Passing secrets with decorator @secure() shouldn't give an error

[MarcosAlanoBairesDev]

Bicep has a decorator @secure() that makes an output be able to pass secrets.
The problem is even using it, I still get an error from ARM toolkit.
Here is the official documentation: https://learn.microsoft.com/en-us/azure/azure-resource-manager/bicep/outputs?tabs=azure-powershell#secure-outputs
Here is the line of code I'm using (Bicep):

@secure()
output accountKey string = storageAccount.listKeys().keys[0].value

Output in JSON:

"accountKey": {
  "type": "securestring",
  "value": "[listKeys('storageAccount', '2025-01-01').keys[0].value]"
}`

Here is the error:

   NestedTemplate [parameters('storageAccountName')] [ Lines 485 - 776 ]                                                
    [-] Outputs Must Not Contain Secrets (6 ms)                                                                         
        Output contains secret: accountKey    

Since the type is securestring, shouldn't the toolkit consider this as not an issue?

[MarcosAlanoBairesDev]

I checked that it matches with this test: https://github.com/Azure/arm-ttk/blob/master/unit-tests/Outputs-Must-Not-Contain-Secrets/Fail/Outputs-Cannot-Echo-Lists.json, but maybe it should be allowed if is using securestring.
What do you think?