Could be that it got to the specified points to stop at or could be that time ran out? only you would know that answer.
There's no time limit in arena mode so time running out is out of the picture. And I set the requiredscore to 7000 so if I'd have to guess, then I think it's connected to the fast tortoises not being killed. I think in arena mode, you also have to kill those fast ones unlike in timed mode.
Fortunately points don't actually matter when it comes to rewards, you can literally start event and do nothing and get same rewards as getting 4500 points.
Nah they changed it with the latest patch. Like I said, I only got interested in Andor WP now that it also rewards Phirius Shells. So if you do nothing, you get no shells. The more you score, the more shells you get, although still don't know how much is the minimum score you have to get for 30 shells which is the max you can get if you're level 50 and above.
Anyway, thanks for the fast reply. It's just bugging me that I can't get high score in arena mode. But it's not really important since in timed mode I get at least 5k everytime.