yeah you highlighted the most likely solution which is that rather than expand the size for the tree, the tree will either be chocked and die or will be chopped when it grows "too much" for the narrow hole. Neither would ever result in type of long term and sizable canopy that makes a beautiful, and climate controlled, public space.
This honestly epitomizes the attitude of the seaport that keeps me away from it as a lifelong resident of the city. It feels like a playground for the rich and tourists* and actually pretty hostile to urban life in various ways.
*I almost said with no playgrounds but I guess it finally does have a real playground if only on the very edge.