There was never a question of residency, although some airlines inferred that. It was a question of where the ticketing agent was based.

Oneworld certainly could have put in a residency restriction but for whatever reason they did not. (Maybe it would be totally impractical to require all oneworld airlines to enforce a local proof of residency at check in; and plenty of airlines still accept cash/cheque/vouchers/etc so making a credit card verification would be difficult.)

However that rule has now been removed.

The new wording about converting the resultant fare is redundant; it simply restates how buying air tickets in a different sales city to the origin city normally works. The fare is converted to the local currency at the rate specified in the daily IATA Consolidated Exchange Rate file.