70 year olds aren't the hottest IT strategists. That's why prez build cabinets to fill in for their areas of low expertise
1st, how do you even build a backdoor after the fact?
They could easily limit which phones the update goes to as updates are never zapped all at once.
It shouldn't put other phones as risk if it's only released to this phone.
If apple's defense is "it puts others at risk" not, "it's too late in this case" that means the govt or hackers could build the backdoors themselves if they decide they want in a certain phone.