It’s so obvious that she was coming up with shit as she went along.

The Deathly Hallows were a huge asspull. Trying to make an overarching story was a mistake, the story worked best when it was “monster of the week” standard children’s fare. That kind of format can tolerate the “I’m going to introduce something new that should have wider consequences and then forget about it immediately afterwards” problems (Time Turners, Legilimency, polyjuice potions, love potions…)

They were intentionally left behind to continue the mission/maintain the website. Lots of people have talked to them, they’re pretty easy to find interviews with.