He was simply responding (quite rationally) to my point about it potentially being related to visa waiver, in which case a return or onward ticket MIGHT be required, even if he has a pending DTV application. The airline wouldn't know about any DTV.
Hundreds have. Soon, thousands. You can stay permanently, other than perhaps a day or two per year. But - careful of potential local tax regulations, if you're in the country more than you're not. Usual thing.