You are correct. It would be misinformation. But MacRumors doesn't moderate misinformation in a post or signature unless it breaks forum rules.
Huge social media sites have a large paid staff who can investigate claims. Tiny social media sites have a low volume of content and may choose whether or not to review it all. MacRumors has a small team of volunteer moderators and a high volume of content. Unless that changes, it would not be practical to add a policy to root out misinformation.
Where moderation isn't an antidote to misinformation, information provided by users can be an antidote to misinformation. Forum members can dispute misinformation in posts and provide the facts to back it up. You can't reply to misinformation in a signature, but signatures aren't seen unless the user posts, and if someone is trying to spread misinformation in a signature they will likely make the same claims in posts.
You are conflating two issues. The hoax rule is enforced and we are not ignoring hoax posts due to staffing issues.
The problem here is someone posting incorrect information about a topic, while not having any intent to mislead, is not a violation of the hoax rule. The staffing issue comes in with you, apart from the hoax rule, wanting us to take on the role of fact checkers. Fact checking reported incorrect information is not something the volunteer staff is able to do.
@Doctor Q touched on this in his post above, but I just wanted to clarify for anybody following the thread, the hoax rule is enforced.
And yet there are clear rules about posting hoaxes. A hoax is a form of misinformation, is it not?