Of course, Sony would claim this. Sony issued this denial only with respect to the particular concern that the FE mount would not be able to support ultra-wide apertures. That is NOT the criticism of an ASP-C dimension 35mm format mount that Canon has come up with. The Canon internal R&D department state that they found that if they retro-converted their M mount into a 35mm format mount that it had negative repercussions on the ergonomics of the lens, making it front heavy, and requiring extra corrective elements i.e. a small and cramped mount means larger, more expensive, imbalanced and front heavy lens.
Fuji has also come up with similar criticism of the Sony FE mount based on what they call the "value angle" which simply implies that the dimensions of the FE mount hinder good lens design. This has also been recently the subject of a thread here:
Here's an interesting one that came out of the recent X system summit by Fujifilm. They came up with something that is called the "value angle" when talkiwww.canonrumors.com
Clearly, it was hardly in Fuji's self-interest to come up with this concept (although it won't stop Sony fanboys from dismissing it as self-interested Fuji propaganda). But it probably represents a fair consensus statement of what engineers within the optics industry overall think of the Sony FE mount.
Again, if retro-converting an APS-C mount into a 35mm format mount was such a fantastic idea (as Sony will predictably claim) then Canon would not have bothered spending a lot of time and money starting a new mount system from scratch, with Nikon independently coming up with its Z mount with almost an identical mount diameter to Canon.
The issue is not the veracity of these comments, but under what circumstances the differences in latitiude for lens design really matter to the key market(s). Yes, there will be some who will revel in the possibility that having a lens closer to the sensor permits better edge-to-edge sharpness, and yes some will love the opportinuties for more compact lens design (let's not forget that newer technology is enabling smaller, lighter lens designs anyway. But how many people will think the difference(s) is important enough to differentiate between marques? My guess is not a lot.
I am just as interested in the fact that Canon has increased the number of electrical contacts in the mount - that suggests that they have some serious technological advances planned, possibly some of those years from now. Maybe those advances are still in the theoretical stage and the contacts are there 'just in case', maybe those advances are on the drawing board or already in place?