I don't know what training you had but to allow this claim to pass without refute is just too much.
I will only speak for myself and my personal experience 25 years ago as a Mormon missionary I was NEVER, not once, told to be dishonest. It was the exact opposite.
I could speak for 100's of others that would echo my sentiments about honesty but will stop at my 40+ years of attending Mormon church 99% of the time.
Never, not once was I ever told anything other than be honest. If you remember that you were taught to be dishonest as a missionary for the life of me I can't understand where or why.
I can tell you what my mormon cousins have said “we are encouraged not to tell everything, it is ok to miss lead if necessary.”