Round trip required?

Entertaining story there in your link.
I got the onward traveler requirement a few weeks ago in Cuenca, Ecuador. They wanted to see my flight to Colombia and then out of Colombia.
The first was easy but I had to log in to the internet to access the ticket back to California. They kept pointing to a posted paper with the airport wifi password but it was broken. So I meandered down to the nearest airport coffee shop where the barista gave me a proper wifi link and confirmed that the "official" WiFi of the airport was most often non-functional. Ahhh, serendipity.