That can't obviously be true except for some certainly specific workloads.
Core 2 was the breakthrough that left AMD in the dust from which it still hasn't recovered to parity. Even if I can't recall the numbers, I fail to remember how the very energy-intensive (high clocked) Pentium 4 could have been faster per clock.
Are you sure you're not thinking of the Pentium 3 to 4 change? After all, Core architecture had more in common with P3, didn't it?
Core 2 Duos were slower per clock than Pentium 4s, I think by quite a bit. It was a real set back for performance when they came out.