No idea why it misses them, but I just found that 3.2.0 has the same problem.

Using 3.2.2, I reinstalled all modules from the zip files, but still no change to the list.

I tried manually adding module definition for the Announcements module, which went on fine.  I then tried adding an Announcements module in a content pane - it worked, but then threw errors when I tried viewing the page.  I didn't make a note of the error, as I am completely wiping and starting again.