Any bulb with switch mode hardware to control the LED drive current will exhibit RF emissions. The cheaper bulb in the original article has linear current cont

Any bulb with switch mode hardware to control the LED drive current will exhibit RF emissions. The cheaper bulb in the original article has linear current control. Inside the ASIC, this could be as simple as a BJT or FET in saturation with a (somewhat) controlled base/gate voltage, maybe with some temperature compensation. The linearly regulated bulb will have less RF emissions, though you could theoretically still have a bit of rf trash from edge effects depending on the rectifier and filter cap. Any bulb that has passed FCC Class B will have an upper bound on conducted and radiated emissions, but you can pass such tests on a wide range of margins, and therefore certification isn't useful to clarify which bulbs have the lowest emissions.