I am sensationalist..that is true. I very much enjoy sensations.. don't you?
90% of all users will never touch a PPA? Is that an emotional shoot from the hip estimate or is that a fact based analysis? I'd rather like to avoid emotional statistics if at all possible. So if you can back that up with some verifiable data analysis, please do so.
I do not question that PPAs serve a useful purpose. Having users out there making use of each and every version released by an upstream developer is a very good thing. One could argue that having as many users as possible testing the newest releases as they become available maximizes the benefit to upstream developers. This is at odds with the stated benefits of cross-distro syncing for "preferred" versions. If every release that upstream developers make needs testing..then every release needs to find its way into the hands of users for widespread testing and feedback. Having distributions stagger what they distribute is one way to see a continuum of release testing.
If all the major distros version lock you are more likely to get boom-bust testing cycles where a lot of bugs go unnoticed across multiple releases instead of a flow of bugs and fixes for each upstream release. The natural feedback loop of the release early release often model is at odds with the concept of preferred version-locking.
Perhaps the reality is the fact that version locking that some distributions feel compelled to do for stability reasons is the underlying problem and not the solution. Since upstream development for many projects moves at a fast clip, the multi-year promise by distributions to keep versioning static retards the natural feedback cycle of release early release often that upstream project development makes use of.