The article doesn't use the words "proof-of-work" -- it's the person who posted it to HN who gave that title. But I see the analogy.

A proof-of-work currency (1) prevents uncontrolled inflation or devaluation, (2) should be difficult to generate the currency (i.e., a lot of work), (3) but easy to check the currency (i.e., check that the work was done).

The Somalias presumably have a threshold of quality at which they'd accept a fake shilling. I'm sure they wouldn't accept a blank piece of paper. They probably wouldn't accept a black and white photocopy. At some point, the quality is good enough[a] that they'd accept it even knowing that it was not produced by the government.

That satisfies the basic idea of proof-of-work: (1) It prevents out-of-control inflation, (2) involves a fair amount of work (professional printing), (3) but you can decide at a glance if it's good enough to accept it.

[a] Just for interest, this is what a real one looks like: http://banknote.ws/COLLECTION/countries/AFR/SOM/SOM0037.htm