Fair enough. But it still gets its word from the physically printed word on the outside of the craft.
But at what point does it do that?
This is the first plausible explanation for why "the machines didn't wipe off the plaque" that I've seen, really. They didn't clean it because although they apparently recognized the data files as information, they attached no significance at all to the plaque itself.
So, after absorbing huge amounts of visual data from Starfleet computers, much of which associated sounds with these visual patterns (hell, a couple of closed-caption movies would do it), V'Ger finally looked at images of the original probe and did the same with the patterns on the plaque. Which were still only partly legible. And then named itself "V'Ger," just moments before sending the Ilia probe over to Enterprise.