Not sure what you have been reading, but this is not an official echo feature.
Echo has a new location feature, but all it does is let multiple Alexa devices know which one is the closest to you and then that is the only one that will answer you so that they are not all talking at once. But they don’t know anything about where your lights are.
At our house, we handle this by having different echo groups for different devices. And you can put a device into more than one group. But each group has to have a unique name.
So you can have a group called “Michael’s bedroom” and another group called “David’s bedroom” and then you can say “Alexa, Michael’s bedroom off” and it would turn off those lights. But it’s not that the echo knows where it is, it’s that you defined the group.
I don’t know whether you can do anything more with location with AskAlexa, @MichaelS would know. But what you described cannot be done with the official features, although a lot of people would like to see that.