Yeah the IAAF doesn't consider Duplantis as an American athlete. His dual nationality status is irrelevant, he chose to compete for one country and that's all the IAAF accepts until he decides to go through the IAAF process to represent another, such as the USA.
If the USA decides to take Duplantis' record and have it as the US record then that's up to them.
I don't agree with it because you can't represent two countries at once in this sport, but USATF is free to enforce any and all crazy rules they want.
It would be similar to Somalia trying to claim Farah's records to make themselves look good. They can do it if they want, but nobody actually thinks they are Somali records.
In athletics, Duplantis is only Swedish.
A fact that gets confused amongst many fans on this site (all the 'American born' highschool/college/senior record nonsense).