There has been many topics on this matter on ozb, whirlpool forums and many more, and I just contacted DJI earlier for the 100th time to clarify once again.
They said as long as the overseas seller is providing 1 year warranty (should mention this on the listing) then you will be fully covered with the purchase of DJI Care Refresh. Care Refresh purchase must be made through DJI and not through another site.
Also been confirmed by DJI here https://forum.dji.com/thread-108407-1-1.html
Care refresh is for crashes only though, or non-warranty issues, and is only valid in country of issue. If your bird develops a issue you didnt cause (eg gimbal malfunction) and its deemed a warranty issue, you need to send it back to country of origin.
Unsure how it would go though if you sent it in via care-refresh locally and its deemed a warranty issue for a drone purchased as a grey import.