Answer
In the Developer Help, some of the ESRI samples use methods that are flagged 'This method is intended for internal use only.'
Methods marked as 'for internal use only' were created for use in testing by development. They are unsupported methods, and as such, they should not be used. If these methods are used regardless of this fact, be aware that they are unsupported and ESRI cannot be responsible for any problems that arise from their use.