While this is the "standard" macOS App structure, it is not the only one that works.

IIRC, you can put stuff in arbitrary subfolders as long as you configure the RPATHs correctly. This works and passes notarization. I came across libname.dylib in the nonstandard location AppName.App/Contents/Libraries . Not to be confused with /Library or the recommended /Frameworks location. However, there are basically no benefits compared to using the recommended directory structure, and none of the 100+ macOS apps installed in my system have a /Libraries directory.

AFAIK, and not technically relevant, but iOS is very strict on this when submitting to the app store, and they’re not at all clear about it either, i had some very confusing and frustrating errors with self built frameworks with dynamic libraries. You also seem to be forbidden to use .dylib and must use the .framework format.

It’s picked up on submission automatically and not at review, but is a completely undocumented requirement.