Earlier quoted context omitted.
On an otherwise empty page? Yes, it is extremely likely when combined with the payload delay. If you manage to make a single tab commit that much memory as a delta without Flash (remember, 13 MB to > 400 MB) please screenshot about:memory and get back to me. The scroll bars on the tab are revealing, too. I may be guessing but it is an educated guess. Additionally, there were multiple claims so I would not call that s…
No, it's not extremely likely. Given that most browser exploits utilize some sort of a heap spray, a growing memory usage is almost standard pattern for a browser vuln.
There is evidence that this is Flash. However, since everyone seems to want to attack individual parts of that evidence without applying Occam's Razor, I concede it could be something other than Flash. It could be Java, too. It could be a "standard browser exploit" too, whatever that is. Could be cosmic rays too.
The tendency to look for ways to prove me wrong with an alternate theory (which yours is) as opposed to acknowledging that multiple theories are possible with zero evidence aggravates me among technical people. In the absence of a disclosure we are both right.