The article states "XAVC Long GOP and XAVC-I All Intra 4:2:2 10-bit," and I feel this could be interpreted in multiple ways. It is important to point out that this camera cannot record 4:2:2 10-bit in XAVC Long GOP.
Let's hope not.
No, if you really wanted to take full advantage of using EF mount lenses, you would put a full-frame sensor in the camera. As it stands, their 4K model with a speedbooster will give you a wider field of view, shallower depth of field (at equalized field of views), and more light - and it's half the price. And you can use the same lenses. Unless you have a "need" for 6K, this product doesn't make a whole lot of sense.