Lots of performance issues with both types. They are PR stunts but they do want to put them into service. Also 4101 hasn't ran on the 57 in service it was just a simulated run.
Also about the hybrids, originally they were meant to be used only on the 72 but now that is no longer the case. They just get assigned to the 72 like 99% of the time because that's what has been happening for years now.