Very good question. Because many individuals don't reach such a monumental milestone of going over 100, it generally gets a question mark. We want to make sure.
Also, aside from the false suggestion Jelena suggested (which is spot-on), there is a category you can use too to add them to the centenarians group. See this page: https://www.wikitree.com/wiki/Category:Centenarians
In fact, by Wikitree standards, if the profile has sources to support it, they would be Supercentenarians - an even more exclusive list of people who lived to a ripe old age! See the above link for more.