Do not rely on this functionality due to the time limits mentioned below.
You can force a device to attempt to report its location by sending a special notification.
automation - alias: Notify iOS app trigger: ... action: service: notify.ios_<your_device_id_here> data: message: "request_location_update"
Assuming the device receives the notification, it will attempt to get a location update within 5 seconds and report it to Home Assistant. This is a little bit hit or miss since Apple imposes a maximum time allowed for the app to work with the notification and location updates sometimes take longer than usual due to factors such as waiting for GPS acquisition.