basically the asymmetrical nature of hexagons means attacking from left to right forces 2 tile weapons to spread their damage over multiple targets and is more advantageous to melee weapons, while attacking from the top or bottom or at an angle lets you focus more pole arm attacks on a single enemy. enemy hp values aren't balanced around this much focus fire.
pic related illustates the concept, fights rarely end up like this and it's mostly just dancing around trying to outsmart the computer, but compare it to how regular frontlines clash against the enemy and note the ways pole arm can react to changes. black monolith top side weaponizes hexagons in this way
a few properties are being exploited
1. three billhook attacks kill mostly everything
2. enemy AI is aware of 1 and is terrified of entering a tile that puts them exposes them to potentnially 5 billhook attacks and 2 frontline tanks that all get 3 bro surround bonus
3. not entering the surround bonus pocket means being tanked by a shield bro
4. the AI is aware of 3 and doesn't like be tanked like a raid boss, so it will try to flank the sides
5. flanking means wasting all your AP on doing no damage and the player can convert this advantage in action economy to get free hits in due to mastery pole-arm AP cost. dogs and nets help buy more time and you can be obnoxious with footworks and pathfinder.
the goal is to put the AI in an impossible situation where all the options are wrong which makes it easier for you to bait them to run around wasting AP on futile attempts at flanking that divide the enemy into groups that are too far apart to help each other so you can attack one while zoning the other. very fun and safe way of playing, like the full adrenaline style you can grind most enemies while taking minimal chip damage to lower expenses and avoid morale penalties from suffering injury or morale decay from needing to rest.