JCC Jr. is the bigger name there, JCC Jr. had been announced as the main event long before any of the other fights had been put together.

Also Calderon just faught, this was like a stay busy fight for him and TopRank IMO needed some names on there they added Arce immidiately after and then Calderon came next. I think Calderon himself understands what happened and was $willing$ to fight as the undercard.