Having a heterozygous deletion is still effecting the right gene. Without knowing both of her parents genetics it’s hard to say if it was natural. What he did could produce either a heterozygous or homozygous result on the gene, but only the homozygous presentation is effective at prevention.
So 1 was a full success and the other showed activation on the appropriate gene, but not enough to confer resistance. Although it is possible it does since he used an artificial gene. We know the natural one is not effective in a heterozygous presentation. I still think that was his greatest mistake. He should have just used the naturally effective gene.
You do make a good point with the full backing rigor of the scientific method this procedure would always be successful.
I didn’t say it was magic. Part of the issue is we don’t know what modifications he made in making his artificial version. I won’t pretend like there aren’t a lot of unknowns there. It could alter the effectiveness in numerous ways.