When a browser supports dynamic imports it is shimmed like this:

self[importFunctionName] = new Function('u', `return import(u)`);

This is incorrect because the URL is no longer resolved relative to importing module, but relative to the dynamic import polyfill file instead. This is a problem for example loading modules from different on a CDN.

Ideally we would have access to the importing module location, so that urls can be resolved transparently relative to the importing module with new URL(id, importer), then there is no need for setting a module directory.

Without that, I think the urls in native dynamic imports should be resolved relative to the module directory so that the behaviour is identical to the behaviour of the polyfill.