For those who got the 10,000 welcome points and have been on a peasant-tier subscription since then, these extra 2,500 points could push your balance out to 15,000 points, enabling you to quality for 2 free Google Nest Minis.
I don't quality because I set up direct calling as soon as it was available, otherwise I'd have enough points for that deal :(
I hope this helps someone else.
To be clear: this allows people who have a mobile phone with Telstra to make calls from their Google Home. Boost reportedly works too, but they don't get Telstra Plus points.
Official Instructions for setting up Voice Activated Calling are here.
I don't have a Google assistant enabled device to avail this offer :(