I’ve noticed the past couple of times I’ve run Sceptre echoes that, for some reason, hats are included in the rewards afterward. In this screenshot, you can see that there are 4 sceptres and 5 primalist hats. If what I’m looking for is sceptres (which, actually, I am at the moment), this lowers the pool of possible items to choose from - in this case, by over 50%.
This is the echo I just ran.
I’ve only noticed this so far with sceptre nodes, but I’ll keep paying attention now (and turning my loot filter off after completing an echo) to see if it happens other places.