To have the full approval of Rome, they had to sign it either now or before the diaconate. I
assure you +Fellay and assistants signed it a long time ago personally or the Romans would not be so "gracious" to them.
Canon 833, Nos. 5-8
obliges the following to make the profession of faith: vicars general, episcopal vicars and judicial vicars; "at the beginning of their term of office, pastors, the rector of a seminary and the professors of theology and philosophy in seminaries;
those to be promoted to the diaconate"; "the rectors of an ecclesiastical or Catholic university at the beginning of the rector's term of office"; and, "at the beginning of their term of office, teachers in any universities whatsoever who teach disciplines which deal with faith or morals"; and "superiors in clerical religious institutes and societies of apostolic life in accord with the norm of the constitutions."
See the canon 833 on link below.
http://www.vatican.va/archive/ENG1104/_P2R.HTM