Looking at the exceptions for getFolderTree (3.3.1.3) it seems that this should raise a constraint exception if the input id is not a folder. Same for getDescendants, getChildren, getFolderParent, and getObjectParents when the input is a folder (not just non-fileable) - probably others.

Or is it expected that these methods will raise objectNotFound in these cases? (if so, objectNotFound in 3.1.4.1 should note that it also applies to ids which are not of the expected type)