Just finished my coffee and saw your post this morning.
You’re right-on about this – and in my experience, almost all libraries only want you to provide a link to check out your tracks – and privtae links work well for this.
Having a private link in bandcamp or soundcloud allows you to group your tracks by genre or instrument (or however you wish) and creating “albums” that can only include the tracks you want a particular prospective library to hear.
There’s a topic here on the forums about adding a “preview” voiceover to protect your tracks.