Yes, it could involve multiple attractors. I'm not sure which kind of symmetry you refer to though. Do you mean some sort of radial symmetry comming from everything else towards a unique set of values? Even in that case it would not be symmetric because the acceleration (force) would be different from different regions, due to for instance the stuff in (2008 Boyd Richerson and someone else).
Imagine the Lefties, who value driving on the left - and the Righties, who value driving on the right. Nature doesn't care much about this (metaphorically speaking, of course), but the Lefties and the Righties do. I would say that was an example of moral symmetry breaking. It may not be the greatest example (it is more lilkely that they actually care about not being killed) - but I think it illustrates the general idea.
About your main question, no, that is not the same as instrumental Moral Values. Those who hold that claim would probably prefer to say something like: There are these two sets of convergent values, the instrumental ones, and about those we don't care much more than Omohundro does. And the Convergent ones, which are named such because they converge despite not being for instrumental reasons.
I suspect they are practically the same. Intelligent organisms probably won't deviate far from Universal Instrumental Values - for fear of meeting agents whose values more closely approximate them - thus losing control of their entire future.
Lefties and righties is just a convention case, if humans had three arms, two on the right, there might have been a matter of fact as to coming from which arm preference things go better.
I think this fear of other agents taking over the world is some form of reminiscent ingroup outgroup bias. To begin with, on the limit, if you value A B and C intrinsically but you have to do D1 D2 and D3 instrumentally, you may initially think of doing D1 D2 and D3. but what use would it be to fill up your future with that instrumental stuff if you nearly never get A B...
Stuart has worked on further developing the orthogonality thesis, which gave rise to a paper, a non-final version of which you can see here: http://lesswrong.com/lw/cej/general_purpose_intelligence_arguing_the/
This post won't make sense if you haven't been through that.
Today we spent some time going over it and he accepted my suggestion of a minor amendment. Which best fits here.
Besides all the other awkward things that a moral convergentist would have to argue for, namely: