The idea that someone had childhood trauma that appears a few decades later, whether over the course of two years or a day doesn't fit the bill of psychogenic amnesia, but yes for sure, that is a real aspect of dissociation in mental disorders which involve it, like bipolar 1 or BPD.

As far as the James Chu study, I'm not sure what to make of it since it would seem to be saying repressed memories is a thing, but no one seems to cite this study much. I can look up the guy and see the book it's excerpted from and that he has testified on some criminal cases as an expert witness but something about it all seems dubious. Because why wouldn't this guy be in the spotlight otherwise? Would be interested to know if anyone tried to duplicate his study.