All sources I can find provide a similar explanation to each phase.
In the Selection Phase, we start at the root and choose child nodes until reaching a leaf. Once the leaf is reached (assuming the game is not terminated), we enter the Expansion Phase.
In the Expansion Phase, we expand any number of child nodes and select one of the expanded nodes. Then, we enter the Play-Out Phase.
Here is my confusion. If we choose to only expand a single node, the nodes that were not expanded will never be considered in future selections as we only select child nodes until a leaf is reached during the Selection Phase. Is this correct? If not, what am I misunderstanding about the Selection Phase?