What happens if you define DATETIME2 columns as Nullable in Temporal table ?

CREATE TABLE Employee
( 
  [EmployeeID] int NOT NULL PRIMARY KEY CLUSTERED
  , [Name] nvarchar(100) NOT NULL
  , [ValidFrom] datetime2 (2) GENERATED ALWAYS AS ROW START NULL
  , [ValidTo] datetime2 (2) GENERATED ALWAYS AS ROW END
  , PERIOD FOR SYSTEM_TIME (ValidFrom, ValidTo)
 ) 
 WITH (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.EmployeeHistory));