A datasheet from Tobii says the gaze data rate of IS5 is 33Hz(fine gaze) / 60Hz(fast gaze):
https://cdn2.hubspot.net/hubfs/1995689/is5/tobii_is5_evaluation-kit_data-sheet_v3_20190925.pdf
So, what is the benefit of a lower data rate? Stability? Or “optimum tracking over a large population”?