According to the source, they claim the entry level rMBP 13 2016 features DDR3, while the rMBP 13 and 15 with Touch Bar 2016 will feature DDR4. That can't be true? Apple lists all models with DDR3 on their websites. But they also lists the SSD of the entry level to be soldered onto the motherboard, so who knows..
I can't understand the reasoning for going with DDR3 over DDR4? Performance-wise, they aren't all that different. But they use less power, and with Apple's focus on battery life and power consumption, why would they go with DDR3 instead of DDR4? The Skylake CPU's and motherboards should be able to support both.