xliioper

You are misunderstanding. It automatically upfares to a Y fare on the ATL-PVR segment in order to combine the two fares on a single ticket due to the fare rule combination requirements on open jaws. The only way to avoid the high-priced Y fare is to book the flights on separate tickets instead of trying to combine on a single ticket. If you use Google Flights to search for pricing on these multi-city itins, it will automatically tell you to book as separate tickets in these cases in order to get the cheaper price.