I've seen this mentioned a few times on FT. If this is true, then it has changed in recent years. I had an IDC Centurion (UK-issued) and was able to get a U.S. Centurion when I called and asked a couple of years ago, when I was establishing a U.S. address. I did not use Global Transfer as I wasn't giving up my IDC (I downgraded it to IDC Platinum after my U.S. Centurion was issued).

Susan