In short, yes. I'll agree that JWs either are not consciously aware that they're lying or do mental gymnastics to excuse it. When I was a JW I once questioned a few other JWs about saying "we're not here to convert anyone" when someone answered the door stating that they had their own religion. I couldn't understand how they could say that when we were constantly told the goal of the ministry was to start bible studies and to bring people "into the truth." The answers I got were all cop-outs. I heard "no one can convert anyone, they have to convert themselves." I heard "Oh, I know we're told to help bring people into the truth, but I really do just enjoy talking to people about the bible, so that's why I'm out in service." They lie, then they'll find some excuse for why it's not a lie.
Another thing that will cause them to lie is when they just can't conceive of the truth being true. They'll refuse to acknowledge the truth of something if they realize that the implications of that truth chips away at the foundation of their cult beliefs. It's hard to say that they're lying in this case - they believe they're telling the truth because it simply has to be the truth. But that said, they have the means to realize it's not true, so it definitely feels like a lie to an outside observer.