When loading a Singleplayer game all tasks that existed seem to be recreated during load time, but they are not displaying. Hence the player cannot see the tasks (sieze base, build base, etc...) nor assign himself to these tasks. I had one single occasion where only one task was properly displayed, which lead me to believe that the tasks are recreated during save load from scratch, but it seems this is happening too early and the game fails to display them. You can see in the provided video that the tasks do in fact exist, as when I became a commander I had the option to cancel the task. And by default the AI commander automatically creates "Sieze base" tasks at all times.