The new event is being held within the Australian PGA Championship, the 24 women split into groups with the men in a format that had proved popular with players and fans in Brisbane.
That was until the weekend, when a three-horse race for the $180,000 winner's cheque emerged between Oh (seven-under), Sarah Jane Smith and Grace Kim (both five-under).
The trio would normally be grouped together for a Sunday shoot-out and there were late moves to make the change, with officials reportedly meeting to consider the option before it was dismissed.
That meeting came after Oh, who had quizzed the format on Friday, doubled down amid confusion on Saturday.
Seeking her second career win and first since 2015, the LPGA member wasn't aware she had regained the lead for the final round until speaking to media.
"It's going to be hard to know what the score is; I thought there were lots of leaderboards, but there's only one on the ninth and maybe one or two on the back nine," Oh said.
"So if we're doing split groups again for the girls, it's just going to be try your best and see where you end up I think.
"If you know what's going on within the group you might change the way you play, which can be good, can be bad ... which is interesting."
Oh on Saturday won back the lead with a three-under 68 despite a double bogey on the 14th.
Kim held the lead before she too made double-bogey at 15, while Smith dropped two shots at 16 but birdied the last in what became a see-sawing battle.
Oh, 25, burst onto the scene with an Australian Masters win in just her second event as a professional in 2015, but hasn't won a tournament since.
"You lose a lot more than you win in this sport so hopefully I can get the job done; it would be nice to sort of reassure myself," she said.
Kim is hopeful of earning full-time US tour status later this year and beat Oh to win the Sandbelt Invitational last month.
"It's obviously really good to always be up there and to be able to chase someone is pretty exciting for tomorrow," Kim said.
"Hopefully I'll have a lot more putts drop in tomorrow."
