I think the list of those going are not on the critical of Bp Fellay List. They’ve usually been kicked out or moved to impoverished nations.
You may be right.
However, it's possible that there are some who will attend the retreat who are still on the fence. Who knows why more of the French priests of the SSPX do not outrightly condemn or criticize the new orientation of the SSPX since 2012. Surely all of them have realized that the SSPX no longer follows in Archbishop Lefevre's footsteps, and that Bp. Fellay has intentionally taken the SSPX in a different direction. Surely they are afraid of retribution, given what's happened to their confrers who did complain, and perhaps they worry about being disobedient (since the virtue of obedience has been drummed into them), or they believe that Bp. Fellay knows what's best, or that he knows something that they don't. It's difficult to say exactly why more of them have not rebelled against the new orientation.
I hope that some of the priests at least will not be completely brainwashed by the retreat (as the article states), and that they will realize that Bp. Fellay is a traitor to the legacy of Archbishop Lefebvre.