It is always PWM under the hood, the question is, how much was spent (or not) on the filtering network out of the PWM. Is it closer to buck converter or is it straight up flicker at the output.
Actually that's not true, my first thought was "just use a layer of phosphor excited by the LEDs", but fluorescent tubes do that and people used to make the same complaints about flicker, so.
Looks like "flicker index" is a useful(?) search term, anyway.