What is insincere about saying exactly what you want as the end result of negotiations? Bolton essentially repeated Trump when he (Trump)said there can be no deal without the complete denuclearization of NK.
The fat little Rocket Man holds no cards in this game.
It has nothing to do with insincerity. Even if Bolton and Trump are correct, you don’t come out and compare the current situation with a previous one where the guy who gave up his nuclear program was later undermined by the U.S. and assassinated.