This is not a question, but rather a remark. The introduction to CosmosDB might suggest that it offers single digit millisecond latency for synchronizing data between different regions, which is not true. CosmosDB offers single digit millisecond latency for read and write operations.
The latency for synchronizing data between regions depends on the distance between those regions and is limited by the speed that light can travel in a fibre cable, which is approx. 200,000 km/sec. The latency will be higher than 9ms for almost any two regions.
Your observation is spot on. Thanks for pointing out the possible misinterpretation. In a future update of the course I will look at making that clearer.