As a new species, he also won't be able to reproduce with other cultivators at the third mortal coil because he and they will be too different at that point. They will be practically different races.
He doesn't think it is unnatural by any means. He thinks it is just right that humans lose their urges to have sex and fall in love because they don't need to reproduce anymore.
There will be a lot of humans who can't fathom losing their ability to love and reproduce. There will also be many people who don't think losing those two things is a good thing. But as a human who has lived a long life and experienced both of them many times, he thinks they are overrated.
