Thanks for that. I had understood about the satellite not being truly stationary. However I had forgotten the bit about the aircraft correcting for its own speed.
I wonder if the BFO for the final partial handshake was wildly different to the previous ones, which is what you might expect if the correction was not available for this final event. The graph I have seen (included in link below) does not seem to show this final 0019 UTC event.
MH370: What does Inmarsat ping data reveal? | Air Traffic Management | Air Traffic Management - ATM and CMS Industry online, the latest air traffic control industry, CAA, ANSP, SESAR and NEXTGEN news, events, supplier directory and magazine
This link also gives the 0011 data but not the 0019 data
Aqqa on MH370
One thing I noted in this graph is the progressive increase in BFO over time. Presumably this is not because of increasing ground speed, but because the plane was flying an arc. That is, as the plane flew further south and the satellite became progressively lower in the sky, the relative velocity between plane and satellite progressively increased (even though ground speed may have remained constant).