publisher from tutorial doesn't react to simulation time of 1s

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I followed this tutorial (ROS/Tutorials/WritingPublisherSubscriber(python) - ROS Wiki) and everything works fine for real/wall time.

But then I tested the same code with simulation time (in separate windows/terminals):

$ roscore

$ rosparam set use_sim_time true

$ ./talker.py
[INFO] [1688140481.155550, 0.000000]: hello world 0.0

$ ./listener.py

$ rostopic pub /clock rosgraph_msgs/Clock [1,0] --use-rostime
publishing and latching message. Press ctrl-C to terminate

The "talker" didn't react to the updated ROS time. Then I cancelled (Ctrl-c) and I tried:

$ rostopic pub /clock rosgraph_msgs/Clock [2,0] --use-rostime
publishing and latching message. Press ctrl-C to terminate

Then the talker printed two messages for time = 2.0 seconds:

[INFO] [1688140488.717273, 2.000000]: hello world 2.0
[INFO] [1688140488.719683, 2.000000]: hello world 2.0

This is not what I expected.

1. Why doesn't the talker react to the new simulation time of 1 second?
2. Why does the the talker see two messages, when the simulation time is updated to 2 seconds?

ROS environment variables:

ROS_VERSION=1
ROS_DISTRO=noetic
ROS_ETC_DIR=/opt/ros/noetic/etc/ros
ROSLISP_PACKAGE_DIRECTORIES=
ROS_MASTER_URI=http://localhost:11311
ROS_PYTHON_VERSION=3
ROS_ROOT=/opt/ros/noetic/share/ros
ROS_PACKAGE_PATH=/opt/ros/noetic/share