Wentworth's item price history shows recent sale for less than my buy order

I've had a buy order for 500k for an IO for a few days. I checked today to see what the price was like, and there's an entry showing a sale for 20k from today.

I thought the person with the highest buy order greater than than the list price should get the item when someone makes a listing, but clearly this didn't happen. (Or there's a display bug that would likely impact market prices).

Here's a screenshot:

Sorry for the necro, but this is still happening:

This happened on Live too. They were never able to track it down before shutdown. Seeing as it was there from when  Wentworth's was added to the game, I don't think there will be a fix for this.

Annoying yes, but it is what it is.

Do we know whether it was just a display bug or these are real sales that go through in spite of the intended rules?

It has been stated that it is a display bug.  Somehow, it will combine (or completely switch to) sales from other items, but the actual sales occur as intended.