21.6 mm image height refers to half-diagonal length, as does the field of view angle (typically). So it's 43.2 mm diagonal, and thus full frame.
The Embodiment 1 design is F/1.55, so it's closer to F/1.6 than F/1.4. There's quite a number of surfaces right there. There's quite a number of moving groups too there.
The lens length is given as 191 mm, fixed length objective. Front element (glass) diameter is about 86 mm.
EDIT: Personally, I'm not sure what Canon is aiming to do with these objectives, unless it's just to build fences around their market area with patents. Clearly shorter back focal length allows to improve the performance of ultra-wides significantly, allowing either better MTFs (mostly sensor limited) or faster objectives. But the cost is the weight, and I really am not sure if I even wanted to go with that lens. Sigma 12-24/4.0 Art is 125 mm long (lens only), and it's not a small lens, and it already is pushing what I want to carry around. This would be close to the length of EF 70-200 / 2.8L.
With mirrorless full frame camera, I'd be looking at more moderate aperture F/2.0 ... F/2.8 objectives as those would be lighter and smaller, and I'd try to increase the maximum magnification to 0.3x for more general imaging tool. I thought mirrorless was supposed to be lighter?