As per BODATSA (following the latest revision) Hilliardiella oligocephala is recognised as a synonym of H. elaeagnoides. POWO to update.
Swelankomo, N.; Manning, J.C.; Magee, A.R. (2016). 'The genus Hilliardiella (Asteraceae: Vernonieae) in southern Africa'. South African Journal of Botany. Available at: https://doi.org/10.1016/j.sajb.2016.05.010
Unintended disagreements occur when a parent (B) is
thinned by swapping a child (E) to another part of the
taxonomic tree, resulting in existing IDs of the parent being interpreted
as disagreements with existing IDs of the swapped child.
Identification
ID 2 of taxon E will be an unintended disagreement with ID 1 of taxon B after the taxon swap
If thinning a parent results in more than 10 unintended disagreements, you
should split the parent after swapping the child to replace existing IDs
of the parent (B) with IDs that don't disagree.