Direct umd module import returns different result than aliased import

Question

In Vite/Vue3 app I import two identical umd.js files:
One is in node_modules/foo/bar/dist/foobar.umd.js (and imported with alias @foo = node_modules/@foo).
Second .umd.js file is in <root dir>/foo/bar/dist/foobar.umd.js.

Both paths are resolved, but when imported, the module outside of node_modules is not imported correctly as ES module:

import * as foobar1 from '@foo/bar/dist/foobar.umd' // is in node_modules/foo/bar/dist/foobar.umd.js, works
import * as foobar2 from 'foo/bar/dist/foobar.umd' // NOT recognized as ES module

console.log('foobar', foobar1, foobar2)

foobar1 returns named exports (app, pinia, router), __esModule: true and Symbol(Symbol.toStringTag): "Module"
foobar2 returns only Symbol(Symbol.toStringTag): "Module"

Where is this difference coming from?

If it's relevant, this how the alias (for the correctly imported module) is defined in vite.config.js:

resolve: {
      alias: {
        '@foo': fileURLToPath(
          new URL('./node_modules/@foo', import.meta.url)
        ),
      }
    }

Edit. Vite's dependency optimization seems to be affecting this. If I add to vite.config.js:

optimizeDeps: {
      exclude: ['@foo'],
    },

foobar1 is also not returning named exports, but that doesn't help me much.

Answer 1

As mentioned in edited question, apparently Vite's optimizeDeps seems to be the key here.
After adding to vite.config.js:

optimizeDeps: {
      include: ['foo/bar'],
    },

this will import named exports correctly:

import * as foobar2 from 'foo/bar' // works! imports named exports
import * as foobar2 from '/foo/bar' // won't work! (even though the path itself is correct)

It is imperative to use the exact same path as provided to optimizeDeps.include.