To gently split hairs- those in first flight following the field master are staying with the hounds, wherever they might go in pursuit of their quarry. The field master’s job is to stay with the hounds, at the distance worked out with the huntsman, while keeping the field in sufficient order to avoid interfering with the hounds as they hunt.
‘Hilltoppers’ are historically the ‘slow’ group, going literally from hilltop to hilltop in order to observe hounds from a distance, rather than trying to stay on the circuitous route of hounds and their quarry.
In a hunter pace, yes, it should equate to the term ‘full cry,’ because that is top speed for the hounds and the idea behind a hunter pace ‘optimum time’ is meant to be a pace sufficient to stay with hounds in full cry.