"PS4 is equipped with 8 GB of unified system memory, easing game creation and
increasing the richness of content achievable on the platform. GDDR5 is used for this memory,
giving the system 176 GB/second of bandwidth and providing a further boost to graphics
If you really want to nitpick about it you could point out that it only says GDDR5 is used for this memory, and not that it is the only type of memory used. Sony sure made it sound like GDDR5 is used for all 8 GB though.
Anyways this is a pretty pointless argument because (A) there is a correct answer and (B) nobody here knows the correct answer, they are just guessing. Just wait till we learn more about the system. Right now this topic is nothing but people positioning themselves to say " I told you so!!!" when the final specs are released.