Fr. John was very ecumenical and very concerned with the spread, love, and knowledge of the truth, and the unity of Christians. He was not at all irenic - willing to ignore certain truth for the sake of artificial harmony.
Ecumenism is a virtue connected with the love of all our fellow men, and the specific apostolic desire to enlighten those in error. Irenicism is a mortal sin connected with the denial and refusal to proselytize the knowledge of known truths among those in error.
Most persons called "ecumenical" today are really "irenicists", and much "ecumenical" activity is really sinful "irenicism".
I stand corrected. Loose talk on my part. You are of course completely correct.