Also a lot of CI is "start a VM/container, run the build, save the artefacts, wipe everything", whereas the telemetry data is only uploaded every however often;

Also a lot of CI is "start a VM/container, run the build, save the artefacts, wipe everything", whereas the telemetry data is only uploaded every however often; most CI systems wouldn't collect data for long enough to actually send it before getting wiped anyway.