Can iOS use Wi-Fi to get location even if Wi-Fi is off? On Android, if the user turns Wi-Fi off, the phone will still scan for nearby Wi-Fi access points to help determine the phone's location (discussed in e.g. this article). Does iOS also have this feature?
No.

If Wi-Fi is off, the radio is disabled, and it is no longer augmenting Location Services.

Often, you'll receive a message like the following to alert you to this: