“client” here may refer to a backend app server.
So you can have 10-100s of backend servers inserting into a same table without having a single authority coordinating IDs.
Except if you're using a sharding or clustering database system, where the record itself may be stored to separate servers as well as the key generation itself.
In those cases yes. There's still a case for sequential there depending on the use pattern, but write-heavy benefits from not waiting on one server for IDs.
