This is just dishonest. They're not denying the ship because of any of the physical requirements - they're denying it because the crew hasn't completed the necessary training to safely transit the harbor.
> TasPorts had previously indicated Nuyina may be able to pass under the bridge, but only after successful completing of training courses and simulation exercises at the Australian Maritime College.
> The Australian Antarctic Division (AAD) has confirmed that approval has not been granted and the ship must instead travel to Burnie this summer, on the island state’s north-west coast, to receive fuel. This must occur before every voyage to Antarctica.
It had conditional approval to transit the bridge last year but then ended up being sent to Singapore for maintenance work before they had finished. They were performing more trials earlier this year but apparently still haven't completed everything and are needed in Antarctica so are shifting their plans.