That's a fair point, although in this case drawing attention to the shortage would have made it even more newsworthy, and might have made the few greedy profiteers more fervent in their desire to buy up all stock, even as the average person reduced their buying. Appealing to morality works better when each person gets an approximately equal vote. If one arsehole can counteract the good behaviour of 10, that weakens the honest approach.
Whether it would have actually been worse or better I can't really guess, but I do see your point that it might have worked and definitely wouldn't have weakened public trust the way the dishonest approach did, so yeah, I'll concede that was probably a bad call.