It’s extremely intuitive, it’s part of the ‘us-west-2’ region, but an extension in ‘lax’ and it’s the first availability zone there ‘1a’. Your suggestion makes

It’s extremely intuitive, it’s part of the ‘us-west-2’ region, but an extension in ‘lax’ and it’s the first availability zone there ‘1a’. Your suggestion makes no sense, it implies an entirely new region ‘us-west-3’ but with an entirely different naming scheme (no regions have an ‘a’ on the end of them) and the ‘local’ provides zero context about it with no expansion capability.