Frank Pentangeli question

When Michael met with Hyman Roth in Miami he said it was Pentangeli who tried to have him killed in his home and wanted him dead. Roth said Pentangeli is “small potatoes”. Michael was clearly bluffing or looking for Roth’s reaction.

Later in the film, in Cuba, Michael asks Roth who gave the order to kill Pentangeli. Obviously Roth gave the order. But, why is that a point of contention given what Michael told Roth in Miami? Is it because Roth overstepped by going around Michael to give the order and then lied about? Is it because it further exposed the connection between Roth and the Rosatos?