Strong requirement to share the data widely
This is a strong requirement: "In order to enable reviewing of the data, every KDE contributor with a developer account will have access to all telemetry data gathered by any KDE product."
I miss a reason for this precedence exactly for telemetry data and not other categories of KDE's data.
For me it's almost "the data is public", given the policy of becoming a contributor (contributors are not identified in any reliable way). Requiring disclosing the data this way can be called a factor limiting freedom of KDE projects compared to other FOSS projects. It's clear to me that even GNU projects do not use such policy to share project's kind-of-internal data they to so relatively public groups.
It's also a matter of limiting risks.
I would propose alternative: applying for access to the data, with a simple and clear rules codified. Minimum: give a reason and level of affiliation with the project. Project members would be involved in the approval but would not be the only ones that "approve".
Limiting number of people accessing the data would be increase confidence within the user groups and would also help to track the access in case of accidents.
Yes, de-facto publishing the data is indeed the desired result (see e.g. https://mail.kde.org/pipermail/kde-community/2017q3/003808.html in the previous discussion).
There is one reason for this: transparency. This however only works if the data is free of any personal information or unique identifiers. Ie. the idea is to only track things that we are comfortable making public entirely.