Jesus ultimately cares about the judgement of our eternal soul.
Is it a sin to believe in a Holy deception that the reason He made His return unknown and mysterious is to keep us in line - or away from sin? If we are in anxious awaiting that he can return any moment, we are more likely to stick to His way and in result, preserve our soul. I am not saying He is lying, but loves us so much that He will give us any impression possible to keep us away from the Devil or Hell
Does this go against any other Christian belief or doctrine?
Notice how Biblical passages can look like lies but are not. Please read this very good Christian writers article: http://www.christianitytoday.com/ct/2005/october/26.56.html
"He will rescue you from every trap and protect you from the fatal plague. … For he orders his angels to protect you wherever you go. They will hold you with their hands to keep you from striking your foot on a stone." [All Scripture citations from the New Living Translation.]
At first blush it sounds really good, but that day I had to say what I really thought. Through tears I told the group, "I don't get how this is true. He did not rescue us from a fatal plague. He did not keep us from striking our feet on a stone but, in fact, allowed much worse than that."