I have two steam accounts, and I was not able to see anything related to a game marked private from my second account except when family sharing was enabled between the accounts. With family sharing on I could see all private games from my primary account on my secondary (including games which were not installed on the local system).

If you have family sharing on, hold off. Otherwise as far as I know it works as intended.

I worry that this also has a rose tinted glasses effect on early user reviews. The only people leaving reviews for the first few days are going to be the people already invested enough to pay extra for early access, and they may be more willing to overlook issues with the game.