This seems like Déjà Vu?
Valve added Steam Families to the Steam Beta Client in May. And now, it’s ready for prime time in the stable Steam app. With Steam Families, a parent can share games in their library with up to “six close family members.” Multiple people can play games from the shared library, which includes titles that all Steam Family members own. Steam Families also supports playing shareable games in offline mode. Of course, everyone gets to earn their achievements, save their own game progress, have access to workshop files, and more.
What appears different though is the ability to pool the use of available titles. Multiple people can play the same game simultaneously, so long as the shared library has enough copies of a game to play at the same time.
It’s true that for family and friends you’d not be adding and removing people all the time, so I suppose the 12-month rule will also stop this being abused (to some extent).
See https://www.howtogeek.com/valve-steam-family-feature-rollout/