Acording to this study that was used in defining the IEEE 1789 standard
https://journals.sagepub.com/doi/abs...urnalCode=lrtd (paywall) humans can perceive flicker at up to 4.9 kHz (one participant in the study was able to) with the mean (of the study participants) being 2.47 kHz.
One important parameter that is not being discussed is the modulation depth/amplitude (difference between peek and low) which can compensate for the frequency.
For example incandescent light bulbs have a frequency of 100-120 Hz but because the modulation depth is less than 10% flicker is not usually perceptible compared to older fluorescent lighting that had a modulation depth of 30-50% at the same frequency.
So the higher the modulation depth the higher the frequency is needed to make flickering imperceptible. An estimated 4kHz would be needed for 100% modulation depth.
The 1kHz frequency of the Forma frontlight would be more informative were we to also know the modulation depth/amplitude.