I don't know if it's intentional but advancements can be obtained in disorder.
Achievements had a precise order, this is no longer the case with advancements.
I think it's a bug, i even hope it's a bug. If it's not a but, it's too bad for an "advancements" concept.

Example :

• First : Elytra
• Second : Blaze rod
• Third : Obsidian
• Fourth : Dragon's breath

I specify that I'm in survival.