Both the male and female Olive-backed Sunbirds (Nectarinia jugularis) were caught on video (below) stealing nectar from flowers of Costus woodsonii, commonly known as Scarlet Spiral Flag (above).
Stealing here refers to birds obtaining nectar by unconventional means, thus not assisting in pollination.
The sunbirds landed on the top of the inflorescence and poked their sharp bill into the base of the flower to get at the nectar. By not entering via the tip of the flower, the sunbirds bypass the stamens and stigma, thus do not help in pollination.
Earlier documentation may have misinterpret how the Olive-backed Sunbird draws its nectar from the flowers. The current video caught the sunbird in close-up and there is no doubt that the bill was thrust at the base of the flowers (above). Examination of the flower shows scars of earlier forced entries on the surface.
Details of the flower can be viewed at this LINK.
3rd February 2017