You're choosing to interpret "300 % efficient" under the very narrow definition used in thermodynamics.
Then you acknowledge that it is "more energy efficient" than a (almost) 100 % (thermodynamically) efficient furnace, completely contradicting yourself. Pick a lane and take a breath, outside of academic contexts people will "misuse" technical terms (such as equating COP to efficiency) and it does not matter one bit because it is very clear contextually what they mean.