They associate utilitarianism with "the greatest good for the greatest number," and then imagine things like "it is for the good of this great Nation that you be drafted to dig ditches this year" and they shudder.

That shudder isn't necessarily a "confabulation."

I don't think Luke or Greene is saying that the shudder is confabulation. The shudder is the intuitive emotional response. What they're calling "confabulation" is making up a deontological rule, such as "everyone has a right not to be drafted for anything except defense", or something like that, to explain/justify the shudder.