Parkin can either confirm or deny this as he has much more experience, but it's my knowledge that it is pretty common in surprise attacks, people setting up their declare right before the turn flip.
It's common to prepare for war many turns ahead in these games, but the general consensus is that double moves are not permitted either during war, or
on the turn of a war declaration. It doesn't matter whether you think that nothing much was changed when you moved twice in succession - the point is that Plako can't
know for sure whether this is true or not. Half of the point of the "no double moves" rule is not just to prevent people moving units twice, but to prevent giving people any
grounds for suspicion that you might have done something sneaky. Obviously such accusations can make for very bitter arguments indeed.
If you declare war in your proper turn order, nobody can ever complain that you did anything wrong. If you declare war out of your turn order - whether you make any double moves or not - then you give your rival reasonable grounds for suspicion and accusation. It's better to just avoid that, because even if you didn't do anything wrong, it creates unnecessary tensions between players.
I have to say in this case that you've definitely given Plako reasonable grounds to ask for a reload, even if you didn't actually double move anything. I have to agree with Plako when he points out:
Why didn't you declare last turn then? This seems bit unfair to me. There is still plenty of time in the timer. Why didn't you wait until I can see your positioning and declared after I had made my move this turn?
If it truly wouldn't have made a difference, why not just play in the proper turn order and give Plako no grounds for suspicion?
War wasn't declared until 1590 AD. As that is the current move, it would be impossibe for me to have double moved you.
But you double moved in the declaration.
I didn't mean to be last to make the previous move... I was at work all day. The transports were already close enough to attack anyway, nothing terribly sneaky happened in the pre-war turn.
This doesn't exactly inspire confidence, to be honest. So something
sort-of sneaky could have happened?
(See how messy this can get when you give someone grounds for suspicion?

Hence why it's better to avoid it by playing in order all the time during wars and war declarations.

)