Of course it matters.
PD's "10-15%" over BD came mainly from the higher default clocks, if it had been 10-15% IPC improvement, the end gains would be much better.
As it's comparing stock for stock, so you could get one of these new chips being clocked higher, yet having the same headroom, it's faster, but it's end performance when overclocked won't be as high as the quoted figure in that case (As an example)
As said above, we already know the clock is lower. Performance isn't necessarily IPC or clock. It could be the memory controller is much better, or the cache is faster, or the dispatcher is better. Regardless of where the real world gains come from, all that matters is it's there.