Never control the current to smart bulbs with a dimmer, smart or not. The two devices will confuse each other, and you can either shorten the life of the bulb or even burn out the switch. They work differently. The bulb needs to always have full power available to it and then it will control its draw level.
In the case of the Fibaro, the Fibaro itself is always live, but it does cut current to the fitting where the bulbs reside. So it’s exactly the same issue from the bulb’s point of view as a dumb switch. Since the fibaro controls the amount of current fed to the bulbs, it creates the same problem. Smart bulbs need to always have full power available to them, and then the bulb itself will decide how much to draw.
People approach this in a number of different ways. See options 2, 3a, 3b, and 5 in the UK lighting FAQ.