A well-known feature of the auto-battle tactic, for example.

By the way, I recently came across the opinion that this is not a bug at all, but a restoration of justice :) because in a normal battle, 2-hex units stand a little further apart, and therefore this rule should, in theory, be preserved in the tactic, but as we know, it cannot be achieved manually, so the auto-battle comes to our aid :)

Since we're on the topic, I'll add another observation.
In quick battles, it seems that the division into stacks does not occur. Therefore, if you attack a crowd of archers with one angel, for example (I don't know the exact number that can be defeated with this method), he blocks them all in the first turn and wins because of this, but if you conduct the battle manually, they will become at least two squads. Therefore, most likely, you won't hit anyone in the first turn, and you will also take direct damage, which leads to defeat. :(