Honest question, don’t all newspapers do this? Sure there are subjects where they publish articles representing different opinions, but on core issues (to them) there is only so much wiggle room before they will pull an opinion piece.
No, typically a paper with a strong editorial bent would have at least a token voice from The Other Side and ideally the editorial page wouldn’t always be six pieces about the president or his party every day, but that was before we got this clown show renewed for a second season.
Because the editorial authors are employees of the news organization, they must disclose the conflict of interest between their employer and its owner or parent organization and the matter they are reporting on.
Let's say an editorial piece says "AWS is the best cloud service" but fails to disclose that its owner also owns AWS, that would be a breach of journalistic ethics. Similar case here.
Regardless if it's in the opinions sections, if the author/publisher has clear biases, especially financial ones, they're disclosed somewhere in/next to the piece.
You should respect bias in the news as well, so pick a different criterion. Also the substance of bias doesn't become irrelevant just because you expect bias.