Get-PnPAzureADAppSitePermission: how to use the -AppIdentity filter?

[Dzieni]

Not sure if it's a bug or PEBKAC, so I am posting it as a discussion.

Getting a list of permissions using -Site parameter works like a charm:

PS /Users/michal> Get-PnPAzureADAppSitePermission -Site https://contoso.sharepoint.com/sites/MySite
Id    : aTowaS50fG1zLnNwLmV4dHwyMTY2NjNiNy04ZjY3LTRkYjktOWM3OC1lMjcyMTc2Y2M5OGVAYzI5OWQwNWQtODg4Mi00YTQ3LTkzZDMtY2ViMTIyYjhlODI4
Roles : {manage}
Apps  : {Dzieni, 216663b7-8f67-4db9-9c78-e272176cc98e}

But using -AppIdentity returns an empty response.

PS /Users/michal> Get-PnPAzureADAppSitePermission -AppIdentity "216663b7-8f67-4db9-9c78-e272176cc98e"
PS /Users/michal> 

I am confused as it matches an example from the documentation. Could that be related to the PnP connection permissions?