Well...
Seems that it MUST hold the weight of a single person - many times over. Says here that according to SAE J839B document the door latch must support 2500 lbs of vertical and 2000 lbs of horizontal force:
https://www.mokidoorstep.com/pages/faq
So that's that then... at min. 900 kgs of downforce rating it will support my sorry ass many times over. And then some.