I am happy the repo explicitly points out and provides a disable for the telemetry though, that's good enough for me.
[1] https://docs.nvidia.com/openshell/latest/observability/telem...
There is no such thing. The mere act of making a network connection reveals things like your IP address (reveals your hosting provider or even your geolocation for residential/mobile IPs), days and times you use the software, your OS via TCP/IP stack fingerprinting, etc.
The network path between you and the telemetry endpoint is always listening, too: https://en.wikipedia.org/wiki/Room_641A
Don't take chances, give as little as possible. Better to assume you'll get burned somehow and leave it off.
It is not, nor of open source software in general.
In general, the saying is specifically in reference to services provided over the internet -gmail, youtube, whatever. Note that you don't have the right to modify them and share your own copies -they're closed source.
So no, it's not true of Linux, GNU, etc; it's an apples and oranges comparison.