It's a distinction without a difference. All new development is nAWS (native AWS) legacy is mAWS (not sure about the acronym) which is still AWS under the hood and is mostly just a pool of EC2 instances with preconfigured networks. Nothing made in the last five or six years is on maws, and amazon is a micro service shop so things are always being built new. If you joined today there's a good chance you'd join a team without any maws infra

MAWS is “Move to AWS”, the name of the internal campaign to get legacy services into a somewhat-retrofitted AWS environment. It was a single VPC at one point.