Kalecgos is not a “half high elf”, nor does he present himself as one. He poses as, in Kael’thas’ words, “a half night elf mongrel”.
So what you’re saying is that high elves have no free will. They can only mix with humans, and no other races can or will be permitted to mix.
That sounds pretty, uh, racist. The love of Gazlowe’s life is, we learned in BfA, a gnome.