Their English is pretty good, so I would be surprised if this were some sort of translation error where the line should be more like 'we thank our peer reviewers/copyeditors/reference-checkers/etc.' Taking it at face value, that's what it sounds like - some sort of adversarial process, likely with the others writing in favor (although it's possible the opponent group was only assigned criticism and maybe made up by criticizing multiple paper-groups?).

Someone really should ask, since apparently some of them are on Facebook.