They don't flicker because they derive their power from a DC electronic circuit than creates it's own A/C that is in the base of the bulb fixture.
LOL. That was from an off-topic discussion of the windstorms in our area. Even the CF bulbs flicker when the power goes off sufficiently long.
But you're correct about how the lamps work. What frequency range do they use? 20+ kHz? I seem to recall the early ones could be audible, but are no longer.