Probation in the article's context is mostly an artifact of Australia's Fair Work Act and not being an at-will employment country.

For the probationary period the employer can fire you for almost any reason (like in the US) but afterwards there's a procedure involved where the employer has to show cause and give the employee a chance to rectify the issues before dismissal.

It's not like a trial week that last 3 months, it's more regular employment but you receive tenure (or a sort) after 3 months.