It is neither hidden nor spying. The options are prominent in the settings, and both the source code and the policies around what is collection and explanation

It is neither hidden nor spying. The options are prominent in the settings, and both the source code and the policies around what is collection and explanations of how it is used are public. Moreover there is literally a page ("about:telemetry") where you can see exactly what data is being collected and links to all of the aforementioned resources and more. And the data itself (aggregated) is available for viewing at telemetry.mozilla.org. And they blog about all of this, from how the data is used to how you can see it for yourself to what efforts they make to ensure privacy while doing so. To call it "hidden" is either deliberately ignorant or a lie, I'm not sure which. https://blog.mozilla.org/data/tag/telemetry/ https://blog.mozilla.org/data/tag/telemetry/ https://wiki.mozilla.org/Data_Collection https://wiki.mozilla.org/Data_Collection https://www.mozilla.org/en-US/privacy/faq/ https://www.mozilla.org/en-US/privacy/faq/