It may just be media reporting, but the timing of his +ve test, and his behaviour after it give rise to serious questions of truthfulness.
He is a very good tennis player, but not one that I have ever warmed to, and some of his behaviour on and off court has been very poor.
Tennis Australia appear to have messed up with what they told him (Federal versus State rules, rule updates etc.), but more importantly, he appears to have treated the visa application process with contempt. It was potentially the most important Grand Slam ever for him, and he knew there were very strict entry rules, but he didn’t properly check his application? Pull the other one…