Folks, nothing about Vanitas in the manga can be canon. The very suggestion is ludicrous.
Because BBS doesn't
have a manga.
Lol, exactly.
This isn't really new but since this misconception still seems to run strong in the fandom it should be stated as often as possible:
The manga and the novels are two completely different thngs.
The manga, written by Shiro Amano, consists only of KH 1 ( 4 volumes), CoM (2 volumes), Days (5 volumes) and KH 2 (10 volumes) and is considered "finished".
The manga is considered an alternate continuity on its own independent from the main series (read: games)-canon.
The Kingdom Hearts novels on the other hand are written by Tomoco Kanemaki, who is a member of Nomura's actual KH staff (and the creator of the character Xion) and there exist novels for nearly every KH game so far, exceptions being BBS 0.2 and the whole X[chi]-era.
Kanemaki does get some background information and additional "goodies" from Nomura hmself occasionally so unlike the manga, Nomura
is involved with the novels on the sidelines.
Since the novels hold stuff that is not in the games both unconfirmed and
outright contradicting some parts in some cases, the actual canon status of them overall is arbitrary and not confirmed either positively or negatively.
That being said, most people/fans who read them agree that both the novels and the manga arguably do a much better job than the games (and Nomura by extension) in terms of characterisation of individual characters as well as relationships between characters.