While this logic test might indeed work -
it would not be 'applied'.
This is why N.K. could (and did) go public with its nuke program.

Euphemism only works while all parties care to employ it.

So your logic might prevail on starkest level. But that level is rarely reached and the sheer volume of unsorted Yes, but..s guarantees that there can be no overtly cynical 'Reason' ever later uncovered, amidst the camouflage coded-phrases.
Deniability. But, again, N.K. Deniability only works as long as someone isn't able to call you on it.

I admit my prejudice: I believe that language was invented [primarily] so that men could disguise their thoughts from each other.
Quite possible. Whether it was originally or not, today we are innundated with *blab* words. And most people are happy to not dig too far or think too much about the situation. As long as they are warm and fed, it is okay with them.