What I think she's talking about is Guinness's rules for the record when *they're* the certifying body. I've been told (multiple sources) that Guinness will also accept any UMCA certified yearly mileage record using UMCA rules and that no distinction would be made between records set under Guinness or the UMCA. Strange? yes, but that's Guinness for you...
I'm sure what you are saying is not wrong for those entering under UMCA rules and Amanda will have Kurts Guinness record if she exceeds his total, but it's more confusing than that.
Kajsa has been in direct contact with Guinness as she explains in her video - she has been explicitly told she will have a Guinness record (if she exceeds Billie Flemings total)
Only those entering under Guinness rules (which do not allow drafting during the attempt or the use of a recumbent etc) will be able to challenge her record in the future.
There will effectively be two Guinness Annual Mileage Records.
As you say Strange? yes, but that's Guinness for you - I think a lot of people following these record attempts on here, including myself would agree with you.