It might not have been required, but imo it helps a lot with something that is somewhat similar to earlier events.

For example, if there was another tariff placed on some exports from China tomorrow, listing a year and month next to the article title would have definitely helped. Mostly because there have been quite many news articles referencing similar events earlier, so if there was no year/month listed, I would have thought it is just another discussion on a tariff passed earlier this year.

I don't have a strong feeling on it either way, but the default rule of "no year in the title if the article is from this year" actually makes sense and feels appropriate, as it definitely helps with keeping things a bit more standardized and easier to parse.

Sometimes submitters do that to emphasize that the story is current, but you're right that it breaks HN's convention. The default is the current year, so titles don't need that. I've taken it out now.