Additional Platinum Card 20K bonus points offer

Amex currently offering 20K bonus points for adding an Additional Platinum Card @ $195/yr annual fee. I currently have my spouse on a free Companion Card but was considering upgrading her to an Additional Platinum Card to get the 20K points. Terms say that previous Additional Card holders are not eligible for the bonus, but terms don't mention upgrade of a Companion Card holder. Chat support agent said this was not eligible for bonus but I find that hard to believe. Chat support also didn't seem very confident/competent. Is anyone here better informed than Amex Support? Thanks!