Dimmer bypass needed if neutral available?

[JDRoberts]

There seems to be some confusion about the bypass. Although it can be helpful when there’s no neutral, that’s not its purpose. Its purpose is to add a dummy load to the circuit so that you will meet the minimum load required for the dimmer to function efficiently. Without it, LED lights may flicker, buzz, or not turn completely off.

Adam Whistler has a good explanation:

Fibaro Dimmer Module 1 vs Module 2

Hi Simon, The primary function of the bypass is to simulate an additional load, but it can help in other areas too. If you don’t have a neutral at the switch (which most people don’t), some lights can dim a little unevenly without a bypass. It’s generally only cheap ones, it’s pretty negligable and really depends how particular you are about lighting design - most probably wouldn’t notice it, but I’m quite picky. The bypass smooths the dimming curve out a little bit and ensures you get nice, even transitions. The way in which we perceive light is logarithmic, but a lot of cheap LED driver circuits are set up for linear, so the top end of the brightness curve can appear to dim slower than the bottom end. Does that make sense? Kind of hard to explain without going off on a massive diatribe! …

And from the official manual for the dimmer 2:

FIBARO | Home Automation - Smart Home

FIBARO Bypass 2 prevents flickering of the lED lights and glowing of the turned on compact fluorescent lamps.