Looks like, in Microsoft Graph and OneDrive Id for drive and drive item has special internal format:
Id is equal to unique identifier of the user.Id is [DirevId]![ItemNo].Am I right or not?
The statements that are made for the identifiers are:
driveId = Uniquely identifies a drive
itemId = Uniquely identifies an item within a drive
The actual values of the identifiers are documented to be opaque blobs, and so any meaning inferred from them is not guaranteed to work long term, or across all scenarios. A prime example of this is the different values provided from the Business and Consumer services.