So I posted a question on the graveyard of the LO forum, and after a couple of days of silence headed back to Mr. Google to search the Internets again, drilling further down this time. Turns out this bug has been known for a long time, but never fixed. The workaround:
- Click on the Notes tab to get Notes view of any slide
- Click anywhere in the Slide pane (left panel)
- Ctrl-A to select all slides
- Click on the Layout menu in the Tasks (right) panel
- Click on the single Notes layout template there
- Now each slide will appear at the top of its Notes page
Irritating to have had to spend so much time figuring this out...