Sorry for Necro wake, but could not find a peoper Steam family sharing thread to share this sad new development but here goes:
Steam finally block/broke the last exit in family sharing in one small update;
And with that they broke what I liked most about family sharing the ability for me and my son to play a game at the same time. Pre SFS I use to log into my sons computer so that he install my games and was able to play them in offline, then came SFS and I no longer needed to log into his PC as I could just share my game and he could install them. He still could not play them when I was in a game but the easy fix was for one of us to play while offline, no more.
Thank you Steam, with this update you just broke what I liked most about SFS, and that was removing the need to log into his PC, but now you officially made SFS useless to me as I can return to my old method.