Yes, this is reflected in the execution speed of the workloads (vs being an additional thing). Other things making up the potential for being more than a zero

Yes, this is reflected in the execution speed of the workloads (vs being an additional thing). Other things making up the potential for being more than a zero sum game (half the speed) include making better use of the ALU and branch units that would otherwise be waiting for dependencies. On the other side of the scale is how different working sets of the threads can thrash each others cache working sets.