Biographies of Living People", you will find that it is defensive. It is the result of court cases brought against the Wikimedia Foundation or Wikipedians by living people. The result was a restrictive policy that intents to enforce the use of "sources" for all statements on living people.
The upside was fewer court cases and the downside; administrators who blindly applied this policy particularly in the big Wikipedias. Many people left, they no longer edit Wikipedia.
At Wikidata there are proponents of enforcing a BLP explicitly so that they have the "mandate" to block people when they consider them too often in violation of such a policy.
For a reality check; there are many known BLT issues in Wikidata that are not taken care of. There are tools like the one by Pasleim who make it easy to do so. There have been no external complaints about Wikidata so far but internal complaints, complaints about the quality of descriptions for instance, are easily waved away.
The implementation of a "DLP" or "Data of Living People" where "sources" are mandatory would kill much of the work done at Wikidata and will not have an effect on the existing backlog. Killing the backlog removes much of the usability of Wikidata and will prove to be even worse.
In order to responsibly consider new policies, first reflect on the current state of a project. What issues need to be addressed, what can be done to focus attention on the areas where it is most needed. How can we leverage what we know in other projects and in external sources. When it is really urgent make a cost analysis and improve the usability of our software to support the needed progress. And yes, stop insisting on perfection; it is what you aim for, No one of us is in a position to throw the first stone.