As someone who has done FE and organized them, I have two thoughts on this.
First, there should have been a deadline, and anyone adding after the deadline should have been added to a Pixie Dust list. That way anyone who had extra stuff to give could, but no one would be put out.
Second, I have placed deadlines on sign ups and reminded people that sign ups wouldn't be final until X date. Well, people decided that the groups were final before the final date and then we come to find out that people have cancelled or no longer wish to participate when we get to the final closing date. Now people in the group are angry with me because they ordered personalized gifts even though the groups weren't final!
In summary, I don't think you were wrong to be annoyed, but I have lots of sympathy for FE organizers because some people are impossible to please.