Complexity analysis deals with asymptotic cases where N gets arbitrarily large. Sleepsort would take the same wall time to sort [1,2] and [1,2,1,2] - but it would presumably take somewhat longer to sort an array of 1e10 ones and twos, because it's not a constant time algorithm.
On the joke part, sleepsort is intrinsically an extremely funny concept and I think everyone here gets that. But "constant time" has a rigorous/pedantic definition, which sleepsort doesn't meet, so I think for some readers calling it that kills the joke (in the same sort of way that it would kill the joke if TFA's code snippets used lots of invalid syntax).
I'd never seen sleepsort before, so I thought it was funny. ;-)
I like the idea of (ab)using the scheduler to sort numbers.
Now I'm inspired to make my own "sorting" routine, maybe touching filenames and then sorting them with `ls -n`, or rendering triangles and then ripping them off in z-plane order, or stuffing frames into a video and then playing it back.
On the joke part, sleepsort is intrinsically an extremely funny concept and I think everyone here gets that. But "constant time" has a rigorous/pedantic definition, which sleepsort doesn't meet, so I think for some readers calling it that kills the joke (in the same sort of way that it would kill the joke if TFA's code snippets used lots of invalid syntax).