MS has only revealed 3 things about the system, one about each main aspect of it.Re-watched the video and they only mentioned GPU and memory bandwidth, I believe this is because they want a few surprises up their sleeve for the reveal. 12GB would leave them with almost double the amount of RAM available to developers compared to PS4 and Pro. Think Ultra textures instead of Medium for the PS4 and Pro. It would be a HUGE difference, especially in screenshots, where it really counts for comparative purposes.
1. Gpu - tf
2. Memory - bandwidth
3 Cpu - amount of cores.
Anything else is speculation, including 12gb.
No esram is based on white paper leak though.
The only thing I would say about 12gb, is that if it was less, then ms would've come out a long time ago and said that the render is not representative and is just a mock up. But they've knowingly let people speculate based on it. Which would be crazy Imo. I'm not saying the render is in anyway the actual Scorpio board though.