No, they weren't going to any lenght to show that, iirc Leto II and some BG admitted to have memories of many deaths, which would be impossible if those were genetic memories. The only one who legitly could have those was the last Duncan since he was ghola made from the amalgam of genetic material from many previous gholas, and even in his case it was explicitly said he had memories he shouldn't have.

It's just magic.

Which is still complete bollocks, of course. Your genes don’t get continually updated with memory data while you’re alive, or even change at all.

Stay off the drugs, Frank.