Accardo saved Cerone from being killed by Giancana many times.

Joey Auippa would have never made any kind of move against Cerone even after Accardo was gone. There would be no reason for it and it's a complete lie created by Fosco to try and make Cerone look bad.

Fosco operates with a motive. He is not objective and is a con man.

He says those things to try and hurt Jack Cerone Jr. who Fosco feels cheated him.

You can never trust an Organized Crime source who HAS A MOTIVE.