On page 64 of that document is an overhead view of where everything is located, including the visitor centre. I know this is no help to you, as I'm sure you're intimately familiar with this. To state the obvious, it is south, rather than east, of Centre Block, and the tree is not on the footprint of the visitor centre as shown here. I gather something has happened since that time that has been approved through the appropriate channels to extend that footprint.
On April 2nd, 2019. See this statement in context.