There are matches scheduled for practice.
International matches (that too against strong teams) are NEVER meant for practice. There were every opportunity to break this Australia team's confidence (already had a hit by Proteas recently), which is very important before such big tournaments.
Remember how India was decimated by England and more importantly Kuldeep's confidence was heavily mauled just before 2019 WC? Same could've done to Zampa, but rather he's treated as the most threatening in these 2 matches.