[joelkoen]

This line refers to opting in to using your device to collect this data. Apple and Google are taking advantage of their global user coverage by using their devices to collect this data without their consent.

Your WiFi network is broadcasting its presence 10 times a second in all directions. It is well known that you should not put sensitive information in your network SSID, for example, as anybody nearby can pick that up. Hence, you can opt out here instead.

[dividuum]

While most users probably don't realize that they contribute to Wifi crowd sourcing, AFAIR using locations services is opt-in on iOS. So "without their consent" doesn't seem true. The info popup also explicitly mentions the WiFi location crowd sourcing.

[axelthegerman]

Sure but any opt-in iOS user walking past other people's wifi is crowd sourcing those networks without the network operators consent.

Unless they only contribute networks that the device has authenticated with.