This development is a puzzlement, because in animals, cell cloning of this kind sometimes never produces an actual embryo even if implanted in a uterus. Thus, one might surmise that whatever modified cells were generated by such a process really IS "only tissue" that couldn't possibly have turned into anything else even given the most solicitous care known to mankind.
Now there would be one way to test these cells to see if this is really true, and that would be by implanting samples of the cloned cells in a human womb to see if any of them turn into an embryo. But who'd want to be the first doctor to try? Whether the experiment "failed" or succeeded, he or she would be a world pariah.
How will we ever know whether or not the human embryos will grow?
It is never ethical to create human life to be used as property or with the intent to kill. In vitro embryos in general and these clones in particular are caused to begin life in danger of their lives. That's slavery and endangerment of life.
As far as cloned embryos, it's similar to cutting off a man's legs with the intent to kill him *because* he can't run away.