In general problem here is less with that specific road has some innate primariness and user retagged it to trunk despite it not having trunkiness.

Typically it is not about road being discussed and community reaching conclusion.

Rather the problem is that some mappers (especially Temat-Droga) refused to discuss anything and tried to force their preferred tagging. In unending parade of new accounts. Or with flood of changes.
And then tried to block return to status quo by demanding discussion over each change. Or redoing it again in edit war.
So general strategy was to make 6 changes, and hope that people will revert only some or it will end in an endless discussion.
To combat that Polish community at this point expects discussion to happen BEFORE =trunk is edited, otherwise anyone can revert it for any reason.

So it is more about "totally new account appears, makes changes to from =secondary to =trunk in their first or second edit, continues this kind of editing". https://www.openstreetmap.org/user/FILszew/history is one just appeared BTW

So in "more unexplained undiscussed nonsense trunk category changes" main problem is 'undiscussed' part and it may be overly procedural and it is a bit tricky to provide proof of no discussion except discussion not taking place.
On account of it being not discussed proving 'nonsense' is tricky - I would need to start several discussions for that, as these edits being not discussed are main problem.
And that is just too much, whole point of "make discussion first" is to move burden on road class warriors.

Hopefully this answers a bit why I though "no discussion happened, nothing linked in changeset" is considered as offense in itself?

Maybe I am overtouchy and it is perfectly normal newbie edit to fiddle with highway=secondary to highway=trunk on long road distance on the second edit?