Marketplace airs on stations that might happen to also air NPR. It's more like dual booting Windows and Linux on your Dell that has a Windows sticker on it.
APM and NPR are both syndicated content, but it's not quite the same.
The local stations mostly call themselves NPR stations (NPR member stations) and they explicitly include NPR branding (ex - right in the logo for mine: https://www.wabe.org/) and pay membership dues to NPR in addition to content licensing.
APM also has its own set of stations, but the list is much smaller. Plus - basically the only content from APM on my NPR station is Marketplace.
It's "NPR" for all intents and purposes. It's not dual booting, it's like a linux machine running WINE for a single application.
