When we apply this on the PDF export demo, the image are drawn correctly in the PDF:
procedure TForm1.TMSFMXGrid1GetCellProperties(Sender: TObject; ACol,
ARow: Integer; Cell: TFmxObject);
begin
if (Cell is TTMSFMXBitmapGridCell) then
(Cell as TTMSFMXBitmapGridCell).Bitmap.Align := TAlignLayout.Client;
end;