Yeah someone uploaded a whole Swedish tree with only given name and surname along with birth year, and since Swedes had such common names they could be any number of people. I admit I don't look into those in checking for duplicates which is why I spent the last 48 hours going over that 2 year old tree to add birth places and precise dates so people don't risk adding and adding people already in the tree.
Since not creating duplicates is so important for Wikitree, one would hope they would make it easier not to do so.