Not really an assumption - more of an educated guess (I said "suspect"). Yes, you can find video of SOAR guys truly making 2/3 on one line, not to mention some of Eric Teal's mind-blowing video. So of course some folks pull it off regularly.
But, I have done maybe 300 laps in Intermediate group at TMP, and I am just not seeing that from many (any?) of my fellow riders. For example, here is a video from this year. I don't know the rider personally but he is obviously on a seriously fast bike, and the rider is reasonably skilled for yellow group - doing 1:25s with clear track. There is not one lap that he makes 2/3 without doing a double dip.
http://www.youtube.com/watch?v=1v5Lnlu7lZ0
All I am saying is that this is typical (actually, better than average) in intermediate from what I have seen.
Here's a SOAR Rookie Cup race (great video!).
http://www.youtube.com/watch?v=ujhCFAZt2r4
At 0:50 and 2:16, everyone including our man with the camera stands it up a bit between 2 and 3. But those are traffic / passing situations, so surely not representative. On the next three laps (3:25, 4:40, 5:58) our guy has clear track, and you would have to be really nit-picking to say he wasn't taking 2/3 as one corner. Very nice. That's what we are shooting for, yes? On the next lap, (7:15) we get to watch another competitor with clear track negotiate the 2/3 combination. Big double dip.
I'm only posting these examples to clarify what I am talking about. If (like me!) you are standing it up even a little between 2 and 3 before adding more lean to negotiate 3, then there is still room for improvement compared to the guys who really have it figured out.