This news has prompted many critics to question why Swimming Australia didn't immediately announce why Jack was not in South Korea with the rest of the Dolphins team, when it had two positive samples.
The Daily Telegraph's Jessica Halloran said there were "too many secrets and lies", while Channel 9 reporter Neil Breen said "the whole thing stinks".
Todd Balym, who has covered swimming at the Olympics, was another who criticised the decision to stay quiet even after Jack's B sample had been evaluated.
"Surely after a B sample positive on July 19 they should both be compelled to go public immediately?" Balym wrote on Twitter.
"Just read the part where it said within 20 days … wonder if it was requested or suggested they wait until after competition is over to save international embarrassment. And it backfired."
Former CEO of ASADA Richard Ings added: "Swimming Australia seem a little out of their depth on this matter."
Speaking on The Project on Sunday night, Ings said he doesn't believe the murky situation is a "cover up" but added "it's certainly a valuable lesson for Swimming Australia and ASADA".
"Sports globally do announce provisional suspensions because you can't keep a secret when a top, famous athlete suddenly disappears from competition," Ings said.
"I hope the rules change to allow ASADA and Swimming Australia to make announcements in future."
Social commentator and communications strategist Kristy McSweeney was another who blasted Swimming Australia during an appearance on Sky News on Sunday night.
"This is a public relations and political stuff-up of epic proportions from Swimming Australia," she said.
However, Sydney Morning Herald swimming writer Phil Lutton suggested Swimming Australia was not allowed to go public with the news unless Jack consented, which she reportedly did not at the time.
"Both (SA and ASADA) suggesting they are gagged until the sanction is handed down unless the athlete consents," Lutton tweeted.
'BITTERLY DISAPPOINTING AND EMBARRASSING'
Swimming Australia CEO Leigh Russell on Sunday described Jack's A sample positive drug test as bitterly disappointing and embarrassing for the national swimming team, the sport and the country.
Russell reiterated the governing body was unable to go public with the news of the provisional sample unless ASADA or Jack did so first, but spoke about wanting to review that policy to avoid situations like this in the future.
"I do want to say that while an Australian athlete returning an adverse result is both bitterly disappointing and embarrassing to our team, our sport and our country, it does not in any way change the zero-tolerance view that Swimming Australia has, and our continuing fight for a clean sport," Russell said.
"We must not speak publicly … we have some very strict confidentiality agreements in place.
"I think that's a conversation that we'd be interested in having (changing the policy) at a later stage. Particularly I think it makes it very tough for national sporting organisations to be transparent."
BOSS 'DISTRESSED' OVER HORTON STANCE
Many have accused Swimming Australia of throwing Mack Horton under the bus by not telling him one of his own teammates was under a doping cloud before he protested against China's Sun Yang.
Horton refused to share the podium with Sun or shake his hand as he sent governing body FINA a message about the need to clean up the sport.
Sun served a three-month doping ban in 2014 and is facing a hearing with the Court of Arbitration for Sport (CAS) in September to determine if his original not-guilty verdict will be overturned in regards to smashing vials of his own blood when visited by drug testers last year.
Russell said she felt particularly bad when she saw Horton protest after winning silver in the men's 400m final, knowing how awkward a situation he was going to be in when news of Jack's case became public.
Russell said she understood Jack had been planning to reveal the positive A test later this week, after the world titles ended, when it would not be a distraction for the Dolphins. But the swimming boss acknowledged feeling "distressed" when Horton staged his podium protest last weekend.
Asked if she had her "head in her hands" when Horton failed to acknowledge Sun, Russell said: "Yes, it was such a difficult one.
"I absolutely support Mack. He's entitled to say and do on an issue that he is passionate about and we are too. This has not changed our thinking on a zero- tolerance approach or our policy.
"But I certainly was watching Mack (protest), distressed about what would befall both Shayna and Mack in the coming days and week."
Dolphins head coach Jacco Verhaeren did not believe Jack's positive test had tarnished Horton's protest message and claimed the Olympic champion would still have done it if he knew about Jack's test.
"The question is going to be asked, 'Should he have done that?'" Verhaeren said in Gwangju. "I think yes because that is a totally different subject as well. This is about someone standing up for clean sport and we still do that.
"If the meet started tomorrow with this knowledge he would stand there again and if I could I would stand next to him."
Horton has since addressed the drama surrounding Jack, telling Seven News: "I was disappointed to learn late yesterday that a fellow Dolphins team member had recently returned a positive A sample.
"I applaud the decision to immediately withdraw the athlete in question from further competition until this matter is resolved.
"My position remains firm — clean sport must be a priority for all athletes, all sports and all nations."
