Gerard,
Not sure I completely track with what your asking, but I will give it a try:
(a) new
(b) the value of autonumber attributes will be set when the object is created, and will not change with each commit of the object, so before or after commit, the autonumber attribute will have the same value. If you perform a retrieve action before committing the passed in object, you will, I think, get the old values for the entity returned from that retrieve action
I don't think this is a bug, just something to be aware of as a developer.
Mike