The help text says this:

    >>> help(list.index)
    Help on method_descriptor:
    
    index(self, value, start=0, stop=9223372036854775807, /)
        Return first index of value.
        
        Raises ValueError if the value is not present.

Emphasis on *first* index. Example:

>>> L = [0, 10, 20, 33, 0, 10]
>>> L.index(10)
1
>>> L[5]
10
>>> L.index(L[5]) # the same meaning as L.index(10)
1

In your code, when elm has the value 1, it's just the value 1; there's no extra information carried along about where that 1 came from. If elm == 1, then my_list.index(elm) means the same as my_list.index(1).

I'd suggest taking any further questions to either StackOverflow or https://discuss.python.org/c/users/

Thanks for the concern, but I'm closing this as "not a bug". Changing this behavior now would be backwards-incompatible and break lots of people's code.