I really don't like "speculative" design, I find it like games you played where you were a kid where you just made up rules, and could change them at will.
Also doing a take-home test on some speculative designer right now =/
Speculative design has its place, especially in the classroom or on projects where getting buried in the weeds isn't super helpful. I would agree that if you're being assigned a speculative design project for a take-home test for a job, that's trash.