I am sure it has something to do with the fear of losing the Alvarez fight, which Oscar Dela Hoya did threaten if the fight with BJS was to happen.

It's just the best excuse ever to 1- get the money fight, 2- not anger Oscar and 3- make sure that nobody loses his face in the deal (aka especially their team as it would be like admitting they did comply with what Oscar wanted).

Now I hope that GGG is still a bit sore from that fight, otherwise I'd suspect him to be a droid of some sort.