However, the team is proceeding with plans to start Colin Kaepernick against the Saints, a team source told ESPN.
Harbaugh said it serves no purpose to his team and organization to let anybody know what his plan at quarterback is for Sunday.
"We could set our watch here for another 15 minutes and you could keep asking questions and the answers will still be the same," Harbaugh said Friday. "We feel like there's no competitive advantage for us to release that information. We just do not get into what the role's going to be, how we're going to use them, and the specifics of that. It's unorthodox. So be it. That's the way we are going to go about it."
Kaepernick would get the nod instead of Alex Smith, who sustained a concussion on Nov. 11 in a 24-24 tie against the St. Louis Rams. Smith missed Monday night's 32-7 rout of the Chicago Bears during which Kaepernick went 16 of 23 for 243 yards, two touchdowns and an impressive passer rating of 133.1 in his first NFL start.
Asked after that game how he rated the performance of the second-year QB out of Nevada, Harbaugh said, "A-plus-plus."
Smith practiced again in a black jersey on Friday, as he has all week.
A team source told ESPN earlier this week that Smith has been cleared medically after passing his concussion testing.
On Friday, Harbaugh said Smith has gone several days without exhibiting any concussion-like symptoms.
"Alex went through his final test today and will be cleared tomorrow, if tomorrow again there are no symptoms," Harbaugh said. "He hasn't had any symptoms since Tuesday, so that's a real positive."
Smith told ESPN on Wednesday night that Harbaugh informed the two quarterbacks that Kaepernick would take all the first-team reps in practice this week, a move that suggested Kaepernick would start against the Saints.
Harbaugh also said Wednesday the QB for the NFC West-leading Niners (7-2-1) could change week to week, and even during the course of a game.
"Both quarterbacks are looking sharp," offensive coordinator Greg Roman said. "Colin's getting some of the reps, Alex is getting some of the reps, and that's how it gets divvied up.
"As far as specific game plan goes, it'll tilt one way or the other a little bit, but it won't be that different. It's a 49ers game plan. The beauty of having a quarterback like Alex Smith and Colin Kaepernick is it's a great situation to be in. But what's happened up to this point is history."
Kaepernick and Smith did not speak Friday with reporters.
Information from ESPN's John Clayton, ESPN's Ed Werder and The Associated Press was used in this report.