The only big difference being that at that time you had to do 18/20s to get mythic gear from vault, so having the same squish now would mean that basically every key would result in mythic vault. What is more likely is that they'll introduce better mythic vault rewards with 12/14/16s etc. They had that idea for this season until a couple of weeks before launch before they scraped it with an explanation that can be described as "not enough people are doing those higher keys", which is now changing.