I think it was more one of those damned "spirit" of V2 things. Confessions could always be done face-to-face, e.g. at a hospital, a jail cell, a convalescent home, in a war zone, The "spirit" of Vat 2 suggested that sin be de-emphasized and replaced with a more affirming/therapeutic approach, and anything that suggested especial seriousness or gravity or the solemnity of God's justice (e.g. semi-darkened confessionals as durable architectural features of a church) eliminated.
In most parishes' experience, the practice of Confession has dropped precipitously.
I don't know of this was ever mandated by actual Conciliar document.
I don’t know either. It may very well be something that evolved, but it is definitely something that became common after Vatican II.
I’ll look into it though.....
I can’t seem to find when and how face-to-face started after VII. It’s not in the documents as far as I can tell, but exactly who started it then?