that sounds strange for a sailboat designed to keel a lot. And the unbroken mast has higher leverage, yet the boat keels without capsizing. And capsizing is usually not that great an issue too.
In high winds removing the mast should make it less prone to capsizing just like reefing would.
EDIT: Oh I see they're thinking it's the waves not the wind.
https://www.morganscloud.com/2008/08/01/sailboat-stability-c...
Overall, the topic of sailboat stability is complex enough that books have been written on the subject: https://books.google.co.uk/books?hl=en&lr=&id=o3edvBByudgC&o...
I would not dive into conspiracy theories on the basis of whatever back-of-an-envelope intuitions you might have here.
>Counterintuitively [a boat with a tall mast] will be be more capsize resistant, capsize is a dynamic phenomenon and increase mast height provides a vastly disproportionate increase in roll moment of inertia which resists capsize. Stability is a static phenomenon even when the boat is moving thru the water and provides little if any resistance to capsize.