I agree. I made a retro claim in January one year when there was chaos in LHR in December of the previous year. I got rebooked on a non-Skyteam flight and claimed the miles for the original routing. I indeed needed (a part of) these 10000 miles for keeping my status, and the miles routinely showed up for the date of my flight. So I kept my status.
(It would have been different if I had not got rebooked to another flight in December, but on a flight in January. In this case the miles would have counted for January.)
IMHO retro claims are one of the two reasons why status is valid till the end of March. (The other one being the time it takes them to send out the new cards.)