Searching for a constituent in the API versus the UI

When a customer of ours searches for her name in Raiser's Edge NXT she picks up 3 records one of which is hers, one which is very similar (middle initial is different) and one other whose last name is the same but it has an “e” on the end.

However, when I use the search endpoint in sky API i.e.

it only returns two of the results and excludes her actual record.

Is there any reason for this? I would have thought that the SKY API search would work the same way as the UI search but it does not appear to be the case.