Is it possible for someone to hack Stellaris online?

So... I played a game and at a certain point a player declared war on me. i scouted his army and it said it was 40k and he had tier 3 plasma/disruptors/armor/shields. so i avoided him and went for his planets with my 25k fleet while he took mine. his warscore skyrocketed even though we both took the same amount of planets. Then I looked at his fleet again and suddenly it was 20k and my fleet was suddenly 60k. At this point I was very confused and tried just going after him, but he beat my whole army without losing a single ship or even breaking his shields all the way.

My fleet and armory composition was strong and should have been perfectly on par with his. The fact the numbers changed so drastically so suddenly for no reason was also strange. Also the amount of warscore he gained by capturing planets was astronomical even though i took his core worlds too. It just didnt make any sense and while I am very hesitant to cast this accusation, it was so ridiculous and unexplainable it looks like he almost had to have been tampering with the numbers. What do you think?

TL:DR An online player's fleet power and warscore were vastly disproportionate to the apropriate numbers. Could this have been hacking?