Based on this "Join user experience program" is turned on by default. It's quite a name for a spying toggle
I own an OP3. This option was available after the Nougat update on my device. When you setup your device, you get a full page about this which has an agreement linked to it and you can disable it before completing the setup. IMO they did asked for it. I've read the agreement but it doesn't specify that they'll collect data like Phone numbers, Mac IDs, WiFi SSIDs, etc so they're definitely wrong there.