Because D11 is the last best hope for 100% spotbeam coverage, I'll bet that spots are their primary concern. If they have to tilt the satellite to get the right coverage, they don't want to lose CONUS in the process.
Note that even when D10 was considered nominal all along, there were problems with some of the spotbeams that may or may not have been fixed. This is their chance to cover those problems (assuming they still exist).
I would think that D12 going up next year would actually be their last best hope but I do get your point about why it may take a while to light D11 up.