When you start your PowerCLI session with the provided shortcut, it will execute an initialisation script.
In there the different PowerCLI pssnapins are loaded.
The core pssnapin also initiates the vimdatastore psprovider.
Together with that provider there are 2 new functions (New-DatastoreDrive and New-VIInventoryDrive).
The vimdatastore provider also intercepts the Datastore parameter on the New-PSDrive cmdlet.
So you can do
$ds = Get-Datastore -Name MyDS
New-PSProvider -Name ds -PSProvider vimdatastore -Location $ds -Root '\'
but also
$ds = Get-Datastore -Name MyDS
New-PSProvider -Name ds -PSProvider vimdatastore -Datastore $ds -Root '\'
But the functions that are added are even easier to use
$ds = Get-Datastore -Name MyDS
New-DatastoreDrive -Name ds -Datastore $ds
And I admit, the documentation on the psproviders and the added functions could be a bit better.