It's also obscure what really gets sent to Microsoft, and what not. There was a Linux based OS that warned the user at every single application trying to phone the internet[1], even Gnome Calculator.
There is no reference to GNOME calculator in that page.
Given the extraordinary claim, please link better proof. I cannot imagine GNOME calc phoning home, unless you crashes and you have manually enabled debugging telemetry post-installation.
Fetching currency data is not phoning home. And how is currency conversion supposed to work without contacting an external service?
Let's not dilute the original meaning. Phoning home means sending telemetry and other usage data to its creator and associated third parties, and this data exchange is not at all necessary for the program to do its job.
Communicating with the Internet without express prior consent, with as much emphasis as I can convey in the limited formatting options provided by this site, ABSOLUTELY IS PHONING HOME. Any other assumption is unsafe and a privacy hole large enough to deliver freight.
If the calculator wants to pull exchange rate information, all it needs to do is ask. Anything else should be presumed as shady in the current environment.
Note that in the example shown in the website, Gnome Calculator is not phoning home, but imf.org; probably a benign thing; it just showed how much control one can have over one's computing.
[1] https://subgraph.com/index.fr.html