At one time, this was true. But with later versions of Visual Studio, which included the ability to add multiple items from a single template, the return value for this method could not return multiple items. So it now returns a NULL value in all instances. This is due to the contraint that the COM signature for this particular method cannot be changed without breaking a lot of code already in use.
Consequently, if you need the ProjectItem interface of the item just added via the AddFromTemplate call, you can either iterate through the ProjectItems collection, or you can create a ProjectItemsEvents.ItemAdded event just before calling AddFromTemplate, and store away the ProjectItem passed to your OnItemAdded handler.