No they didn't. You are drawing the line at act, as the 1973 SCOTUS drew the line at viability, while the authors have made the case that potency is criteria enough for knowing that a blastocyst is a human being, who, by its very nature, has intrinsic worth.
If one continues along your line of thinking, the line for establishing when one is a human being can erroneously be drawn anywhere. For example, the age of reason is generally placed at age seven, but a seven year old usually doesn't know how to drive a car. Although seven year olds can't drive cars, they have the potential to learn how. Furthermore, five year olds, generally speaking, have the potential to reason, and drive a car as well. Depending on where the line is drawn (and the agenda of the one drawing it), there can be a justification argued for offing 5 year olds, 7 year olds, babies with only their heads unborn, and anyone else who doesn't meet the established criteria.
Such lines of establishing who is a human being are always subjectively and artificially drawn, and humans are killed if the one with the agenda does it in secret, has a good PR campaign, or has enough power.
At any rate, the true answer lies not in act, or viability, for that matter, but rather in potency.
I say we draw the line further back. A woman has eggs with the potential to become human, all it requires if fertilization. A man has sperm with the potential to become human, all it requires is fertilizing an egg. Any waste of egg or sperm should be considered homicide.
Why not? All it takes for a blastocyst to achieve its potential to become human is successful implantation in a uterus. My examples just take it back one step further in the process.