Kia ora Elli,
It turns out to be a little more interesting than just an oversight - I received this from WCC today:
"Lena Gardner was originally interred into plot 46 F Public 2, then under licence in 1947 she was disinterred from her plot due to the plot never been purchased. She was then reinterred in between the plot rows and her original plot was then sold on.
The disinterments were done under a licence that was issued by the Department of Health, they put a notice in the newspaper advising families who had not paid for a plot to either pay the fee or disinterment would take place.
If you do visit Karori Cemetery if you find the Van Boxtel plot, Lena is interred behind this plot."
"In regards to George Gardner and Annie Cook they are only people interred into plot 75 E in the public section."
Interesting, but perhaps not a huge help genealogically...