IMHO, seems like the HR is trying to protect the ppl from others who may be trying to research data , yes this is public info, but why are you so interested ( makes one apprehensive) also how would you feel if someone did this to you.
as for Joan, if she wants to tell that is her place to tell, ( this is considered " Office Gossip" ) this could lead to job lose
might be best to keep from gossiping at office, glad things worked out for the best, but be careful they will be watching to see if it's a habit