They've done it once, can't see why they wouldn't do it again.
And yes, even a Pixel running Open Source software isn't the silver bullet. There's always trust in using any mobile device, it's just about limiting your exposure in as many practical ways as possible. The alternative being, as you correctly suggested, is to not use a phone at all.
https://www.phonearena.com/news/apple-sued-for-tracking-its-users-using-native-ios-apps_id143657