Who would need to press the power button to actually turn off or restart the device, right?
The setting to change this is also pretty much buried under Settings -> Special Features -> Gestures.
(Yes, I have no idea why the Assistant is in German when the phone is set to English either 🫠)
Technically it opens your default assistant. Mine is set to Dicio, so it opens that. Also, it wasn’t default for me, but just an option I found while exploring settings.
It seems like they haven’t changed the setting retroactively for existing users, but I just reset my Nothing Phone 1 to factory settings and then it got set by default.
I just got a OneUI update to V7 on my Samsung and it remapped the power button.