In its own coverage of the news in the Style section, The Post reported, "The decision has roiled many on the editorial staff, which operates independently from The Post’s news staff, a long-standing tradition of American journalism designed to separate opinion writing from day-to-day news coverage."
If the intention is to separate news reporting from opinion writing, maybe the opinion pieces shouldn’t be published in the same document as the day-to-day news coverage.
Maybe they shouldn’t try to establish that “The Washington Post endorses X candidate”, but should refer to it as “The Washington Post’s editorial board endorsed X candidate”.
That would be, as per their self declared mission, the truth of the matter.