From the article:
The response times collated in Sydney were tested against measurement instruments loaded onto the cloud platform to isolate whether delays were attributable to the service itself or the latency involved with accessing US-based data centres from Australia.
We all know that all of Australia share limited pipe to outside world.
Of course it will clog during the business peak hours! It's like reviewing the sports car by driving in traffic jams around city and then writing an article that sports cars are slow!