You read one intention of the quotes right. But they are also intended to be scare quotes; if the result of an "optimization" is equivalent to the behaviour intended by the programmer that also worked with earlier versions of the compiler, it's a real optimization, if not, it's miscompilation. E.g., "optimizing" a bounded loop into an endless loop is not a real optimization.
You read one intention of the quotes right. But they are also intended to be scare quotes; if the result of an "optimization" is equivalent to the behaviour intended by the programmer that also worked with earlier versions of the compiler, it's a real optimization, if not, it's miscompilation. E.g., "optimizing" a bounded loop into an endless loop is not a real optimization.