Alexa Groups and Device Names

I would like to use the Alexa Groups feature togehter with my openhab Dimmer items tagged with “Lighting”.
According to this documentation: (sorry, german… ) I can create a group with name “Living Room” in Alexa and assign a Dot to it as well as the devices. If I say then switch the “Light” in “Living Room” on, all Light items are triggered. However Alexa does not recognize my Light items from openhab if I just say “Switch Light on”. It only works if I use unique names like “Light Living Room”. Is it like that or am I doing something wrong?