Google and Apple transmit telemetry data, notwithstanding the user explicitly opts out. Google on Android smartphones and Apple on iPhones on iPhones have been in question for a long time. Study by Douglas Leith shows how Google is capable of receiving data from smartphones even without having logged in with a Google account. While Apple also has access to the users data but, when it boasts privacy, they do so for some reason when compared to Android smartphones. When the smartphones remain at idle state or inactive, Googles Android continue to collect up to 1 MB of user data in every 12 hours.”]
Source: https://gbhackers.com/googles-pixel-apples-iphone-track-transmit-telemetry-data/