There's the problem. Opus Dei is not a secret society. It would never have been confirmed by the Holy See if it were. It is hated by liberal governments in Europe and dissident Catholics in America because it is a strictly orthodox organization in the Church which is having an effect in it's apostolate.
The "secretive sect", "controversial", etc. ad naseum, labels are applied to Opus Dei as a scare tactic. Reminiscent of claims against the Jesuits in early 20th Century America.
There's the problem. Opus Dei is not a secret society.
So is it not 'secretive'? And was Beckett wrong to describe it as such? (I'm asking...I don't know the answer.)