I personally don't believe it. I think someone who diets down (like Da Freak who dieted for his contest) is simply more likely to avoid gaining much fat again. Having already built a solid base of size, it simply gives the impression that he gains more lean body mass. The reality is, he has gained back around 30lbs in about two months after the contest. That is simply how I have seen the body work in terms of bulking and dieting and then gaining again. Your training of "on and off" is what stands out more than anything. You sound like nearly everyone else who is not consistent. I don't train on and off. I have trained consistently for years. Obviously, my body will respond to that if I were to diet down strictly. I have noticed significant gains in the past by doing so once returning to gaining and I wasn't always under 15% body fat when I went back to gaining size.
I think you "bulked" wrong in the past if you truly put on that much body fat. I am not the type of person who really cares about being under 10% body fat unless I was trying to compete. In fact, my personal limit is keeping my waist under around 40" when bulking. All else seems to fall into place. Obviously, our genetics are not the same. I have a large wide frame and you need to find your own limits as far as what you will deal with.
Beyond all else, someone who can't even train without it being "off and on" shouldn't be "bulking up" much to begin with. That action is for those who will still be in the gym a year later, not for those who do this as New Year's Resolutions only to drop out months later.