On this playthrough, my rogue decided to go with the light armor branch of smithing, just to see how the armors compared. On other playthroughs, I went for the heavy armor route to get to the daedric perk. I thought I'd try to get to the daedric perk from the top (as opposed to to the bottom), or stepping down from the dragon perk once I got it.

It's not letting me do this. Is this a glitch, or do I have to come at it from the ebony perk?

Nope, it's not a glitch.

You have to work your way up from the bottom all the way through the Heavy Armor side of the tree.