The kind of intrusive cross-site “we want to know evetyrging you do on the internet” style tracking that focus blocks is completely different than the minimal application usage telemetry that it collects.
Focus increments a counter if you search. With no way of knowing who you are, what you searched for or any way to correlate it to other telemetry.
Pretty sure they will get your IP. If you use any other Mozilla product, chances are they know who you are. And they can correlate it with other telemetry data. Not saying they do, just that they can.
The biggest problem with this line of thinking is telemetry data _can_ be used extremely effectively to "serve you better".
Denying the ability to collect telemetry data for privacy conscious products is to deny them the ability to improve their products using data-driven approaches that have been proven to be overwhelmingly effective in practice.
This would be an extremely heavy handicap, and could very easily make a tangible difference in the prospect for any such product to gain the market share and the resulting network effects needed to become and remain competitive with products and companies that couldn't care less about your privacy.
So at the end of the day, condemning companies like Mozilla who clearly make a serious effort to collect only the most essential and non-identifiable metrics to improve their product can be quite counter-productive if your endgame is for privacy-conscious apps and companies to be as successful as their mainstream counterparts one day.
It collects things like "how slow is rendering" or "do you use feature X?". It's all anonymized, and you can verify this from the source (you can also turn it off). Folks are very careful if adding new telemetry metrics.
I'm okay with telemetry, if it makes Firefox better. It's a way of 'paying' for Firefox. Your trust has to go somewhere eventually, and Mozilla doesn't seem like a bad option.
IIRC it is pretty anonymized already. I don't recall the details.
Also, Mozilla's privacy policy explains what Mozilla can do with the data. Generally it's not a matter of trusting the company as much as it is believing they'll follow their own privacy policy, which IMO is a reasonable assumption for most companies (including Facebook and Google, which use your data but do tell you about it)
I'll add an anecdote as a counter-example (I think the details might be a bit off here, it might not be VS):
Visual Studio removed 'macro' functionality, and a bunch of developers went to the forums to complain and demand an explanation.
That explanation was as follows: None of those developers enabled "send usage feedback," so the usage statistics for macros was close to 0%. The developers sensibly thought it made sense to stop supporting that feature.
There's a tradeoff associated with extreme privacy, and perfect is the enemy of good.
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.)
The data that is sent doesn't contain any relatable information, but you still have to connect to the Mozilla server to deliver it which in turn could be associated with the content you sent.
Mozilla unlikely does that right now, but they have to advertise truthfully nonetheless. Even if the reason is merely that people won't turn on that feature otherwise, there is no need for us to tolerate such hypocrisy.
Why not do privacy properly? Then the first comment in any conversation won't be well, there is that in-house telemetry.
The hypocrisy to advertise "tracking protection" as a key feature and then send tracking data to your own servers is hillarious.