They kick up a fuss and ask you for 'survey purposes' (lol) how you got hold of the number because they're trying to expunge it from the internet as much as possible. As it was explained to me (via a small lecture, though they ultimately helped me), that number was meant for use of Guarantors to call up Passport office in the event that they missed their verification call and they aren't really equipped with the agents to drink from the firehose that is all passport applicants trying to find their status.
Having said that though - you do you, decide if the means justify the ends.