This is one of the those times where Player A outdoes Player B, but Player B comes up with a countermove, to which Player A responds with a counter, and finally to which Player B's real plan comes into motion after foreseeing everything that would happen. Usually you can spot these type of scenarios easily if you're into manga like Usogui, but this is one of those times where I honestly couldn't tell who was getting the upper hand. Sako Toshio did a good job portraying Lalo as someone who was on the verge of losing and Arata as someone who was becoming some final boss material.
As for Amen intervening back there, I'm under the impression she only interfered like she did because she was actively enforcing the rules, which is what Woodchipper pointed out early about how "one can never go further than the posted Ban cards." Kakerou is operating under the mindset that players cannot leave the Ban area, which to Kakerou involves them acting as a mediator upholding the rule that players cannot leave the Ban area in the utmost manner. This isn't a scenario where Kakerou will allow players to violate a rule and then be punished, this is more like Kakerou doing what it can to make sure no player violates any agreed-upon rules by word; if a player somehow happens to violate a rule, then it's Kakerou's failure and their collection time for that player's life. I feel like this is a topic that's been discussed several times and has several variations in previous chapters. Most notably, the match between Usogui and tacky suit guy over vials of corrosive acid comes into mind since Kyara stuck by Usogui by not bending the rules, but by supporting Usogui as far as the rules could allow Kyara to not interfere.