Your opponent was inactive for too long, that should not lead to an automatic loss.

[sevenseas]

Matches that are cancelled by inactivity are not counted towards the head to head statistics.
So 'winning' a match by your opponent going inactive will not net you a win versus them.

But what if they 'become inactive' because they are down Marshal/General etc

They could avoid the loss?

It counts as a win. 

It's only on the first move (and second move I think?) where inactivity results in the game becoming null and void.

It's a very poor idea from the developers, as people can exploit this to pick and choose who to play against. People have done this on purpose to avoid playing against me, then surprisingly (!) we managed to get paired again immediately after the first match was declared null.