The specific formatting specifications are requirements of the American Medical Association as part of the trademark.
On page seven of the AMA Booklet, the following explanation is given:
“The phrase ‘AMA PRA Category 1 Credit’ is a trademark of the American Medical Association. Accredited CME providers must always use the complete italicized, trademarked phrase. The phrase ‘Category 1 Credit’ must never be used when referring to AMA PRA Category 1 CreditTM.