getTagConfigsAsync with recursive true

Regarding getTagConfigsAsync API, does anyone know how the recursive parameter works? Does it only read tag models of its children or traverse sub directories? If it collect from entire directory tree, is there a performance concern?
https://files.inductiveautomation.com/sdk/javadoc/ignition81/8.1.8/com/inductiveautomation/ignition/common/tags/model/TagProvider.html#getTagConfigsAsync(java.util.List,boolean,boolean)