It just makes it look like they had no plans or ideas for the summer event gear and when dungeon gear does becomes dyable, it's usually not until the next expansion. All crafted levelling gear from 50-56 (new in HW) and 60-66 (new in SB) have once been dungeon pieces.

I also vaguely recall the devs (or Yoshi-P himself) saying it takes them around 6 months to design new gear.