I've just had a look at the preview for the tutorials on recording drums. All look pretty good as per usual for this place. I have to question, however, the Decca Tree tutorial.
That doesn't look like any Decca Tree I have ever come across!
The Decca Tree is usually a three mic arrangement for stereo recording. It is highly favoured by engineers recording large ensembles such as choir or orchestra - though by no means limited to this application.
The decca tree has also seen some adaptation particularly in the areas of surround sound recording where extra microphones can be added to pick up rear and side information.
I'm sure mic technique you describe is a perfectly reasonable way to go about recording a kit with three mics, but a Decca Tree it is not.
The only relation I can see to a Decca Tree is the number of mics used but thats about it.