I can see that this issue has been raised many times previously (eg https://community.spotify.com/t5/iOS-iPhone-iPad/Can-you-quot-save-quot-an-album-without-saving-ever...) but haven’t seen a definitive response from Spotify about whether you can add an album to Your Library without it separately also adding every song on that album to Your Songs.
I agree with all the previous comments that it is really annoying and wonder whether Spotify have any plans to address this?
Updated on 2019-07-24
Thanks for sharing your idea here in the Community!
However, this has been implemented with the recent new version of Your Library we rolled out. You can find more info about how the new Your Library works in this Spotify Answer.
Hope this helps clarify things! If you have any questions, don't hesitate to give us a shout.
Have a lovely day 🙂