“Power On Behavior” means you get to choose what will happen if your power is cut and then restored.
The Phillips hue default is intended to handle emergencies by turning all your Hue lights on to full power white. And that’s what happened before this choice was offered.
Now, you can choose whether to take the default or to have the bulb return to whatever setting it was at when the power was cut. That means if it was off, it’s days off. If it was blue, it returns to blue.
When this was originally announced, they said you would be able to make this choice for an individual Bulb, for a room in the hue app, or for all lights connected to that bridge.
This is a really nice feature if they deliver what they promised. It means you can keep the bedroom lights from waking the kids up in the middle the night, but you could still have your own light come on Bright in case you want to investigate the state of the house because a power failure occurred. ( that’s something we would do in my house because of the medical equipment.)
But the main point is, the choice is yours.
However, I haven’t confirmed if they actually delivered it in this format or not. It appears that the update may have been released in Europe first.
Just updated and there is now firmware for the first gen br30 lights that was not available last week (and not in release notes). 126.96.36.199581 for lct002.
The lightstrip, lux white (lwb004), and earlier white ambiance (color temp) bulbs (ltw004) , don’t support power on behavior.
By the way, over the last couple of days most of my hues have updated and now have the functionality. In particular all my lwb004 are all set (which I have a ton of). Only missing are my two first generation ambiance and color. It does look like they are following through on their promise to eventually provide the update to all Hue bulbs.
Note - the 4 Ikea bulbs I have on Hue don’t have the functionality and I don’t expect them to. (Which seems obvious).