R-tree insertion procedure when leaf is full
Nope, you are wrong!

In your example, if you keep adding nodes to the leftmost entry, the splits propagate upwards. There will be more levels, but as they propagate upwards, the leafs are always in the same level, thus it always makes a balanced tree, as long as you make sure you follow the insertion and splitting rules tightly (e.g. make sure there are always $m$ minimum objects in a node)