If the trials for the vaccines - on which their approval is based - had included groups who were only given one dose, and it could be seen that it provided some protection, even if that were somewhat less protection, then I think it could be quite appropriate to decide to decide to go with a one-dose approach if it meant that overall you could protect a larger number of people in a shorter time.
But as far as I understand, that wasn't included in the trials, so this is using the vaccines in a way that hasn't been tested. Maybe there is enough knowledge about how similar vaccines work, that it's legitimate to be confident that the results will be predictable, but it does seem to me to be wrong in principle. After emphasising to everyone that careful test procedures have been gone through, and no corners have been cut, to then appear to be happy to kind of make it up as you go along - I don't see that it is good for general public confidence. I wouldn't quite say that it's definitely a bad move but I don't feel very comfortable with it.