And that's a good thing
Yes considering some 970's were built on as a low as 670 based PCB's.
Facts are the OcUK 970 with the 980 PCB and components rarely if ever suffers from coilwhine, a similar finding also with NVIDIA 980 reference 980's also rarely suffering from whine.
NVIDIA build a card to a specification designed for that card with a set cost.
Then board partners get cards and most in general look for ways to reduce cost as the board partners have three options when buying from NVIDIA:
1. GPU only
2. GPU + memory
3. GPU + BGA + Memory (Complete card)
So when board partners are buying option 1 or 2 from NVIDIA they then look for ways to decrease their manufacturing cost to either hit a lower more competitive price or just increase their margin.
Of course they also sometimes increase quality, for example Classified, HOF, Platinum and Lightning cards as examples.
I've seen some pretty shocking cost downs in my experience such as very low cost and cheap VRM's on some cards in the past.
NVIDIA and AMD build a card to do the job and a good job, then board partners change spec, an example was 290/290X the AMD reference PCB had far superior VRM's to the ones which MSI used on the gaming cards and the result was I blew quite a few MSI Gaming 290 series cards up when overclocking them to the limit and also mining on them.
Reference is guaranteed quality.