This is incorrect. New does not just mean “new for a user”, it also implies recent.
The consequence is that an item would disappear from a “new” list when it is no longer “new”, no action required from the user (which is not how it works in Discourse).
For an item to disappear from an “unread” list, the user must perform an action.
New defines object-state while unread defines user-state.
If “new” is different for each and every user, it should be called “unread”.
The best “proof” of my point of view that the “new” list should actually be called “unread”, is that when I mark a topic as unread (shift-U), it will re-appear in the “new” list.