(Just make sure you don't sign chromium into your google account. If you sign into your firefox account in firefox, then data is also uploaded, albeit in an encrypted format.)
Yes, Focus uses WebView. On newer Android versions it's actually provided directly by Chrome (Android 6+ IIRC), on older Android's (Android 5) it's a separate package that's still built from the same sources. (Android 4 is more complicated but also not supported by Focus for that reason.)
IIRC there's an option to enable tracking protection in normal browsing on desktop. It's enabled by default in private browsing. (I can't check right now though - it's possible it's just an about:config option too.)
Firefox iOS (on iOS 11+) definitively offers those options, on Android it's private browsing only by default and I don't think there's an option to enable it in normal browsing.
Hypothetical example... but what nefarious things can one do knowing that some anonymous user happens to e.g. refresh pages a lot (or even, how can that data be sold)? OTOH it does let the developers know whether removing the refresh button would affect a lot of users. Or whether moving it elsewhere is sensible (e.g. to the toolbar if used a lot, or into a deeper menu if rarely used).
Sure, this example is contrived. But in some cases features make app development more complicated (ALSA support in desktop firefox might be a better example, but I'm not super familiar with that case). Knowing that a feature isn't used makes it easy to accurately remove crufty/complicated features without negatively impacting a lot of users. And makes it possible to justify retaining complex features that happen to be useful to many users.
Same story with crash reports (typically users have to explicitly confirm sending crash reports in many applications, no idea what kind of system Focus uses though). You need to know which issues are actually important, developers don't have infinite time (as much as we wish we did).
(I used to be sceptical too... but you're sailing blind without this kind of data, and ultimately hurting both yourself and your users.)
Focus (for Android) doesn't use Google analytics directly, but it's an indirect dependency - see below.
Focus does have:
- Mozilla telemetry: enabled by default in Focus, disabled by default in Klar. This only sends data to Mozilla servers, and only concerns what features people use (i.e. do people use share, do people use custom tabs, do people clear using the bin button or the notification). This stuff is used for deciding what features to prioritise (or remove), and doesn't involve Google servers.
- Adjust SDK: an install attribution tool (aka install referrer tracking). This is only used to determine whether the app was installed as the result of a specific (google-hosted) ad campaign. Adjust depends on play-services-analytics. ( https://www.adjust.com/glossary/install-referrer/ ). This only comes into play if you install the app from the play store (which funnily enough Google own). This is the only time play-services-analytics shuld be used, i.e. on first install. This is also disabled in Klar.
(The more interesting question is: could Focus receive the INSTALL_REFERRER itself for ads attribution instead of using Adjust? That data might be meaningless without asking google to tell you where it came from, and they provided it in the first place anyway...)