Hi Mike,
I'm Giovanni from Opencraft. I hope you are doing well.
I could reproduce the behaviour you described on my local devstack.
All the updates posted automatically go to the Updates page, however once the welcome banner is dismissed, it doesn't appear back when a new update is posted.
I'm not sure if the small banner was initially conceived to show all updates, but looking from this perspective, it seems like there's a small bug on the platform.
I haven't looked into this in great detail, but workaround it would be to set the view-welcome-message course tag to True. This can be done with set_course_tag from openedx.core.djangoapps.user_api.course_tag.api, for each user in the course.