That FAQ only applies to customers that did not use the DDO or Lotro account creation tool. Or they used the Lotro account creation tool to make a new Turbine account with a Lotro gaming account now they want to play DDO using the same Turbine account. Or they want a second Lotro account. You have to ask for a product key if you want to add an additional gaming account to an existing Turbine account.
Turbine must have changed something broke the Lotro account creation tool on lotro.com. It reads like all that the tool does currently is create a Turbine with no Lotro account attached to the Turbine account. Hopefully Turbine will get this issue fixed sometime this month after everybody gets back from the Christmas and New Years holidays.
Unless stated otherwise, all content in this post is My Personal Opinion.