No, it's not possible.
Mozilla employees and community members are very talented and capable people, but they are not capable for keeping a nefarious secret :) hehe
The proprietary module (now long removed) is among the reasons the iceweasel project was born (not the debian one but the GNU one that has been renamed icecat when debian took over the iceweasel name).
It is a known fact that for years 90% or more of mozilla money came from google in exchange for making its search engine the default including tracking through an additional parameter in the URL.
There is waterfox a project to build a firefox version free of the mozilla tracking and crap: https://www.waterfoxproject.org/
Disabled Encrypted Media Extensions (EME)
Disabled Web Runtime (deprecated as of 2015)
Removed Pocket
Removed Telemetry
Removed data collection
Removed startup profiling
Allow running of all 64-Bit NPAPI plugins
Allow running of unsigned extensions
Removal of Sponsored Tiles on New Tab Page
Addition of Duplicate Tab option
Locale selector in about:preferences > General
There used to be a collection of privacy patches to remove all the tracking, leaking and privacy issues but I can't find it through web search, it seems to have been replaced by https://github.com/williex/firefox-privacy
Mozilla insist it is health report, analytics and telemetry which is marketing words for tracking and spying.
Do you have a reference for this? The Wiki page, and the project application, seem just to refer to a desire to avoid non-free plug-ins:
> ALL GNUzilla Programs will basically BE Mozilla Source Builds, with the major exception being the implementation of NO proprietary softwares, including plug-ins, according and adhereing to the GPL.
(http://savannah.gnu.org/task/?4529). That's certainly not inconsistent with what you said, but it seems a stretch to deduce what you said without some other reference.