Completely incorrect. The EB engines produce prodigious torque, at very low RPMs. The 2.3l EB motor in the s550 makes more torque, at a lower RPM, than the 4.6l V8s, as well as more HP. And with lighter weight, you don't need as much.
This is not to mention, that for performance driving torque is not always a "more is better" issue. The real issue is traction, getting power to the road. More torque (power) down low just means more wheel-spin off the line.
Serious super cars like 458s have very little torque (in comparison to their HP numbers), at high RPMs, and yet still manage 0-60 in 3 seconds.
AND, since you can't buy a 5 year old 4.6 in the 2015 Mustang, you'll want to compare the driving experience on the two engines on your list.