Is there a simple rhetorical term for implying something untrue by qualifying clauses?

Not all loaded questions contain a contradiction with reality and are unanswerable.
"Did you break less windows today ? " (than yesterday.)
You could answer "No ! " and not say anything that is a lie.

Of course if you just say “no, not less”… the listener could infer that you did break windows …

One classic piece of civilservantese is “we were, perhaps, economical with the truth”.

That was my first thought too. An example of “exception that proves the rule” would be a “No parking 9-5” sign, which implies that parking is allowed before 9 and after 5.