Scripting : UnorderedSet unable to erase variant

Trying the following in DO v13.7.2, it seems that I can't erase an existing value (in this case an Item object) from an UnorderedSet.

var item =DOpus.FSUtil().GetItem("D:\\test\\new folder\\sample.png");
var uset = DOpus.Create.UnorderedSet();
uset.insert(item);
DOpus.Output(uset.count);
DOpus.Output(uset.exists(item)?'Yes':'Nope');
uset.erase(item);
DOpus.Output(uset.count);

Am I doing something wrong?

Probably not. Only works if item is a string. Looks like booleans, integers, and objects can't be erased.