@tomoyafujita
Thank you for your response. I figured it out.
Here follows information for people who run into the same problem:
I can now confirm that the ROS 2 goal_info status codes are equal to the (ROS 1) actionlib status codes (see here)
Also, the messages in /NavigateToPose/_action/status mean a list containing all navigation goals, include old, already completed, navigation goals. The list is sort from newest to oldest entries. In my case, I’m only interested in the ‘current’ (newest) navigation goal, so I always take the first entry in the list. Using the status of the first entry, I can determine whether my navigation goal has finished.