How to upgrade from Marriott Gold Elite (from AmEx Platinum) to Platinum Elite?

My question is if you have an AmEx Platinum Charge Card and you link this to your Marriott Bonvoy account and receive instant Gold Elite status do you have to still spend 50 nights to upgrade to Platinum Elite or do you just need the difference between Gold Elite and Platinum Elite which is 25 nights? Called AmEx and Marriott they didn’t really know how to answer this question.

I believe you have to stay the full 50 nights and there is no shortcut to go to Platinum.