Half Truths and Deceptive Statements are usually more effective than Outright Fabrications, which is why people tend to prefer to use them. They stick to the letter of the truth, but carefully omit aspects of it to violate the spirit of the truth. this is why Kant didn't just say "don't lie" but also "don't deceive" and "don't keep secrets" and "don't omit information", Kant basically tells you to not just tell the truth, but the whole of the truth.