Corner cases in the Interleave Lower Bound for BSTs

The Interleave lower bound is a lower bound for the amount of operations any Binary Search Tree needs to make for a sequence of accesses. It is used in the construction of Tango Trees, and is based on Wilber's lower bound.
The Interleave lower bound is proved by defining a Transition Point for every node $y$ in a static tree $P$.
See Demaine, Erik D., et al. "Dynamic optimality-almost." SIAM Journal on Computing 37.1 (2007): 240-251: Section 2 and Appendix A.

I see a problem with the definedness of the transition point for nodes in the tree that don't have a right subtree, such as leaves, for which there doesn't exist a path from the root that contains both elements from the left subtree + $y$ and from the right subtree of $y$.

Does it constitute a problem to the analysis of the bound?
It certainly seems to weaken Lemma A.1. For any node y in P and any time i, there is a unique transition point for y at time i.
If we consider the transition point of such nodes in $P$ to be themselves in $T_i$ then there is a problem with Lemma A.3. At any time i, no node in T_i is the transition point for multiple nodes in P.

Can the analysis and the bound be kept by not counting the interleaving through the leaves (and possibly their parents), and thus avoiding the need to refer to their transition points?