A C++ comparator must be a strict weak ordering. The three properties of a strict weak ordering is asymmetry, irreflexivity, and transitivity.

Asymmetry means that if $$$a \lt b$$$, then $$$b \not \lt a$$$.

Irreflexivity means $$$a \lt a$$$ is false.

Transitivity means if $$$a \lt b$$$ and $$$b \lt c$$$ then $$$a \lt c$$$.

Your comparator contradicts all three.