If other apps can’t see photos, there’s a problem different than you being able to inspect the package containing the photos database. Any app that needs access to you photos does it through an API and not via Finder. Even Finder uses a photos picker to navigate the storage choices Apple made.
The reason for this is since photos app doesn’t store photos in a manner optimized for file browsing. You are actively discouraged from this to avoid accidentally deleting or corrupting a photo library. If you had managed to access the photos from finder directly, please make a backup of the Mac or photo library and then repair the library.
If it’s important to look at your photos on the filesystem, organized in folders by album or date or another logical grouping, do not use photos.app.
Use something like Photo Mechanic if you regularly need finder access or export the photos to a folder if this is an occasional need.
Apple has a storage mechanism that’s optimized to store the original photo in a database with algorithmically generated unique file names and also optimized for multiple versions of each photo – thumbnails of several sizes, a reduced size (optimize space is how the setting is presented to us) versions of the full size original photo and sometimes not even storing a file locally if it’s stored in the cloud and space for local storage is limited.
