apart from item id there is also bonus id. bonus id determines if it scales to level (there is an extra modifier for the level), or if its fixed ilvl (different bonus id for different ilvl).
the legion dungeon drops already scaled to level, just that they did not have reduced stats when they scaled to a lower level. that was fixed by fixing the stats on the scaled items, which retroactively fixed all the existing items.
draenor items did not scale to level, they are fixed ilvl. newly dropped items scaled to level, so they have a different bonus id from the old items. they can still fix the old items by putting a level requirement on the bonus id, if enough people send bug reports then they might do so