That was apparently misreported, much like most rumors. It was actually the year before this past season, the 2013-14 season that Collins approached Thibodeau, not the FO approaching Collins, according to new information. The FO claims they had no previous knowledge of this meeting, nor attempted to sway Thibs to bring him on. They stated that Thibs kept the conversation private before declining Collins offer of help a few weeks later.
I would put zero stock into the rumor that Collins would now join the staff. I think GarPax is actually going to allow Hoiberg to choose his OWN lead assistants because there is already a built in trust factor with all three parties, something Thibs never really had from day 1. I expect that Griffin will likely be retained in some capacity, as he is a player and FO favorite. Andy Greer was already let go along with Thibs.