I actually think it would be OK if the telemetry were opt-in. At this point, I'd even settle for just having the software actually warn you about the data collection on first use.
We do this (even then, strictly for non personaly identifiable crash/error reporting only), and I would encourage everyone who isn't a friend/family of the team, close community member, investor, etc. not to opt in. It isn't necessary. (Though having a small number of tens of people from those groups who do opt in is reasonably useful.)
As far as I'm aware, the contract of OSS is "you can fork this to change it, if you don't like it" (license permitting).
A big part of the reason people advocate for OSS is so they can read the source code to understand what's going on, and change the parts they don't like. Telemtry sits squarely under that usecase.
I agree that it's good manners for projects made users aware of telemetry, but there's no "contract" that implies they have to.