Victor, this part of the docs explains what you're seeing; scroll down to the

"""
In enforcing reflexivity of elements, the comparison of collections assumes that for a collection element x, x == x is always true ...
"""

part.

https://docs.python.org/3/reference/expressions.html#value-comparisons

In passing, note that dicts indexed by strings (well, indexed by anything) _do_ compare hashes first.  In that specific case it's a major win - but in that specific case we also know in advance that "EQ or NE?" is the only question needing an answer.