Yes - I don't think the word sync should be used for (2) at all. It should just be AddToSkyModel or something. Sync means Sync - not "Include this as another point in the model and adjust the model slightly."
If the mount maker doesn't want to allow a sync of type (1) then the ascom driver could keep track of the sync offset itself - and do the sync for the mount. Then there could be a separate call for AddToSkyModel - and only some mounts would support it.
But none of this helps with my mount issue because I think the sync is fine for me. It's the landing accuracy that's the problem - I think.
If the new code Jared provided works - then all these issues would be swept under the rug - I hope. The mount is just a black box and if for whatever reason it doesn't land at the intended coordinates after a slew - this should handle the problem.
One thing I didn't mention is that for people who do want the mount to sync when centering, it could happen at the very end when the position is within tolerance, and after the last move. It would only need to be done once - and then the ra/dec values in fits would be correct - etc.
Frank