Demon Portal prevents end of combat if..

[Zechnophobe]

I feel like this is a bug, and it has existed for a while.

If the turn order is roughly like:

Unit 1 - unit 2 - unit 3 - unit 4 - Portal troops appear


And unit 4 kills the last standing troop, the portal troops (from the demon portal cast by an opposing hero) will appear afterwards, continuing the fight. It is similar to The Legend where poison could hit one more time before the end of a fight.

Shouldn't battle end be checked at the end of a units turn, not the beginning?