Yes, the current investigation would have followed up on all the Bank Manager's new evidence, no matter how weak, including the TAFE thing. They even checked when the Silverchair gig was on.
Remember there is a HUGE brief of evidence, they have interviewed many people (more than we know!), and only a tiny fraction is brought up in court - they are careful choices.
For example, the kids are cooperating but weren't asked to speak. But the wife was, even though she had no knowledge of Marion or ever met her. Former tips were NOT discussed in court, such as the Armidale College search or Clark Hunter post, but this tip was. This new tip isn't about the details being useful or revealing (they aren't!) but about WHO it's coming from and WHEN, which leads to WHY?
The Coroner will weigh up the value and validity of the alleged sighting. Given the witness had decades to speak up about Marion, it is noteworthy she is only doing it now. The tip itself doesn't identify Marion or her bank transactions, and often contradicts what we know of Marion.
Because the Coroner's job is to determine if Marion is still alive, the Coroner will have to consider the if the witness was consciously or unconsciously influenced by factors such as: reward, need for attention, need to clear her name, media coverage, or other people.