The meetings I've attended in metro Detroit, 'open' meetings are referred to as 'open talks' or 'speaker' meetings, person gets up and tells their story, no on else talks beyond the usual opening remarks. Everyone is invited to attend, and you usually see a fair number of spouses of AA members there.
With one exception, I have never attended nor heard of an 'open discussion' meeting, it was advertised in the local AA directory as a mixed AA/Alanon meeting, we sat on chairs arranged in a 'S' shape, not a table, they started at one end and worked their way down to the other.
Closed meetings in my experience are 'alcoholics only', and they are usually always introduced as such- "Welcome to the closed meeting of Alcoholics Anonymous'.
Last thought, have never heard of an Alanon meeting either advertised or introduced as being 'closed'.