Reloe has discovered that when you cap on Season 4 Aspect crests, you actually get Season 3 Wyrm crests instead — be careful!
In Season 3, Blizzard added a system that allowed you to gain the next available rank of Crests when you were capped for your current difficulty. This made it so that you didn't need to run lower Mythic+ keys or a lower raid difficulty than you wanted to, which was a problem in Season 2.
In Season 4, it looks like this is also bugged and when you're capped on Aspect crests, it's granting the Dreaming (Season 3) version of Wyrm's Crests, which is making Wyrm's Crests much more annoying to come by this season. You can see this in the screenshot by Reloe below.
Hopefully this gets fixed soon.