The topic is https://www.wikitree.com/wiki/Category:Project_Collateral-Prospect
. It still has over 1800 profiles in it.
The profiles you describe probably are connected (as early ancestors) to somebody who supposedly emigrated to New Netherland. (These descendants who supposedly emigrated to New Netherland weren't necessarily Dutch. Many New Netherland settlers were not Dutch.) Most such profiles that I've looked at are unsourced and were created as part of massive gedcom imports in the early days of WikiTree.
At this point, I would think of the Collateral Prospect category as a Maintenance Category. If the person is not Dutch and you've been able to improve their profile, recategorize it, merge it, or etc., I think it would be fine to remove it from the category.