The following is for Photos 7.0 under MacOS 12.6.1, I'm not sure if it holds for older versions.
If you select the photos in an album and hit Command-Delete (rather than just Delete) it will delete them from both the album and the library.
You can confirm this by looking at the context menu: if you right-click to pull up the menu for one or more photos, then hit command while the menu is visible, you will see the "remove photo from album" menu item change to "delete photo". Also, if you select one or more photos and click on the Image menu, then hit command while that menu is visible, you will see the "remove photo from album" menu item change to "delete photo" and the associated keyboard shortcut icons change from delete to Command-Delete.
I just discovered this by accident as I'm used to hitting Command-Delete in Finder to remove files and was shocked to notice the photos I was removing from albums were also being deleted from the library. Fortunately we can choose either behavior.