That was never true. The premise that Romo (or any quarterback) is better when you "limit their attempts" is ridiculously misguided. It is the efficiency that usually limits the need to attempt more passes, not the limited attempts that lead to efficiency. Inefficiency creates the need to throw more.
If what you are saying was actually true, then quarterbacks would get worse as their attempts increase, and that's obviously not the case. In 2014, for example, Romo's passer rating INCREASED as his number of attempts increased. Over his first 10 passes in games, his rating was 111.3. Over his next 10 attempts, it was 112.8. Over his next 10, it went up to 113.6. And over the next 10, it was 126.2. In other words, he became MORE effective as his attempts increased -- exactly the opposite of what you claimed.
Last year, although he missed most of the season, it was pretty much the same. He had a MUCH HIGHER rating on attempts 20-plus than he did on his first 20 attempts in games. Same with 2012. I could go on. Your notion is completely backward.