Adding songs to the library also adds albums to the library in Apple Music

Add and download music from Apple Music - Recommended by Apple

If you subscribe to Apple Music, you can add music and music videos from the Apple Music catalog to your music library. Stream music that you've added over an internet connection. Or download music that you've added to listen to offline.

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• Add music to your library
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• Download music to play offline

Add music from Apple Music to your library

Follow the steps below for your device.

How to add music from Apple Music on your iPhone, iPad, or Android

1. Open the Apple Music app.
2. Touch and hold a song, album, or playlist that you want to add to your library.
3. Tap Add to Library.

How to add music from Apple Music on your Mac or PC

1. Open the Apple Music app or iTunes. 
2. Find music that you want to add to your library.
3. To add a song, click Add button . To add an album, playlist, or music video, click +Add.

Download music from Apple Music

After you've added music to your library, you can download it to your device to listen to offline. Just follow the steps below for your device.

How to download music from Apple Music on your iPhone, iPad, or Android

1. Open the Apple Music app.
2. Add a song, album, or playlist to your library.
3. Touch and hold the song, album, or playlist that you added from Apple Music.
4. Tap Download.

How to download music from Apple Music on your Mac or PC

1. Open the Apple Music app or iTunes.
2. Add a song, album, or playlist to your library.
3. After you add a song, album, or playlist:

• • On your Mac, click the Download button  next to a song or album.
  • On your PC, click the Download button  next to a song or album.

Delete music downloaded to your device

If you want to free up storage space on your device, find out how to remove music that you downloaded from Apple Music.

This may be the expected behavior, but as the OP asked, we want to avoid it because it's a poor design choice that has nothing to do with mangling with metadata. Other platforms, e.g. TIDAL, keeps separate lists of favorites songs and favorites albums instead of lazily try to infer the second one from the first one.

Unless you are able to strip the metadata from the tracks so that they have no album listed, you can't do what you want. If you are using an Apple Music subscription, I don't believe you have control of the metadata.

Yes, that is expected behavior. The track you're downloading has what is called "metadata". This data includes things like the song title, the album title, the track number, the genre. When you add the track to your library, Music sees all of those bits of information and adds them to the library database. So, unless you can remove the album name from the metadata, Music will add that name to the list in the library database just as it adds the track name. And, you can't edit the metadata on music that you're downloading as a part of your Apple Music subscription.