I respectfully disagree with what he's saying for a number of reasons:
- mmWave spectrum hasn't been auctioned in Australia yet and won't be available probably until 2022.
- 4G LTE in Australia is already very fast
- Future 5G modems are likely to be more power efficient
- mmWave is a very high frequency, around 26GHz, and is suitable for very small - line of sight - areas.
Modern phones often cover different frequency bands for different countries. I understand that iPhone 12s include the mmWave 5G bands in the US because there are some places there where 5G is only available on those bands.