Yes, both make sense. In the first case when using Peek() you are not specifying any table, so Peek() will return the last distinct value in the field 'Users', as you will see the values of the field in a listbox. Instead, this line will return as expected (two different values):
LET arg = Peek('Users', $(i), 'tblusers');
FieldValue() returns the value with that index number sorted by load order, regardless whether the value is or is not distinct or unique.
Hope that helps.