Cross shard transactions are supported, but we don't have support for atomic 2pc cross shard transactions, its WIP

Are you one of the developers ? If so, you need to add a specific page explaining in detail the guarantees that this gives.

For example: point 08 says "Assign different tables or workloads to different shard groups" and point 02 says "Split hot shards as workloads grow". How do those interact ? Can a single table be split across multiple shards ? If so don't you need 2pc to enforce primary key constraints ?

The intro pages just read as AI slop.