are StorageMetrics of Folders retrieved using CSOM or Graph?

[MSFT-klpinhac]

The PnP-PowerShell cmdlet 'Get-PnPFolderStorageMetric' is using the following code:
( please see https://github.com/pnp/powershell/blob/dev/src/Commands/Files/GetFolderStorageMetric.cs )

IFolder folderWithStorageMetrics = Connection.PnPContext.Web.GetFolderByServerRelativeUrl(targetFolder.ServerRelativeUrl, f => f.StorageMetrics);
var storageMetrics = folderWithStorageMetrics.StorageMetrics;

and i know that pnpcore is using either the SharePoint REST API or the Graph API - so which one is used here?
Do settings like "PnPContext" / "GraphFirst" make a difference here?