In TSB a human can be in Standing or Sitting mode.
By default the human initial state is Standing.
The Stand task will not change the pose of the human - just change it's mode to Standing.
This mode will have some impact on the simulation.
If the mode is set to Sitting - seated posture prediction will be used to determine how the human is reaching for objects. It will also influence ergonomic analysis, a task performed sitting down may render different "score" from a standing task.
The Wait task - will not change this mode.
Rather it just introduces a waiting time - e.g. making it easier to syncronize tasks created for different humans.