I don't know anything about modulating LEDs, but could that high freq. have anything to do with the quiet but audible whine I hear when the light is on? Seems like it could be 8kish.
Could also be a transformer but since this isn't a high voltage product it's more likely some disk capacitor in the circuitry.
LED driver might have some kind of LC filters on its power input for EMC reasons, but these are too small to meaningfully "sing". On the other hand it may make sense to follow the driver with some kind of reconstruction filter to remove the "high frequency" flicker, but AFAIK nobody does that because it involves costly and large-ish components with significant losses for somewhat questionable benefit.
Indeed, the Casper uses the Ti TPS63021 boost converter, which needs an inductor (L1/L2 on the datasheet sample application). http://www.ti.com/product/TPS63021?qgpn=tps63021