It didn't. He is confusing when Marika ambushed Ryugen and Jinba Peach and then Kouta using Kachidoki to blast Marika.
And which we know she was holding back against him. The only one he actually eeked an actual victory over was Sigurd.
I wouldn't say she was holding back at all during this second encounter. She stated she was holding back against him when they initially fought with Jimber Lemon Arms vs Peach Energy Arms.
But that doesn't mean that she was holding back the second time. As we all know it, Kouta had a
"Kill me!" bounty all over his head for knowing about the Over Lords existence to the point where Sid and Minato couldn't just fool around with him anymore. Sigurd lost fair and square to Gaim Jimber Lemon Arms when he resorted to try and kill him the first time and this time, brought three Automated Suika Arms for insurance. The Ryouma team wanted him
dead, period. They wouldn't want to toy with Kouta now that it's shown that he was able to defeat Sid, not once, but twice. So in that conclusion, I don't think Minato was actually holding back this time either; Sid wasn't also holding back during his Jimber Lemon fight in Episode 21. I mean, given the circumstances, why would they hold back? He is thwarting their plans with Project Ark and now the plan for the Forbidden Fruit. Mitchy also wanted him dead and had Ryouma's team cooperating on his
terms during Kouta's hunt for the Over Lords. Also to that, Mitchy's face when he saw Kouta return and Minato beaten shows that he was very annoyed and he stated he will take matters in his own hands to Minato.
Kouta definitely improved with the Jimber Arms, as Minato stated that it wasn't just the Genesis Core that was making him that strong and he wasn't even breaking sweat. Countering literally all of her attacks and just gutting her in the stomach and slashing her like nobody's business. Compare that to their initial fight where even the Jimber Lemon enhanced ability couldn't help him fight a held-back Marika. In his first fight, you can see that he considered her stronger than Sid and he was extremely exhausted from the fight, trading blows evenly against a held-back Marika to losing near the end of fight and being jugged around until Mitchy shot her. The fact that he didn't need to switch to Jimber Lemon to defeat someone who was regarded to be stronger than Sid/Sigurd and his confidence in that short fight definitely showed that Kouta was wrecking her to the point where she had to resort to her Sonic Volley finisher. Even then, he still won his fight against Marika by blasting her in the face with Kachidoki Arms. So that's a definite victory over Marika.
Taking things into that context of everything I said above, I'm pretty sure I'm not confusing anything at all, Eldar.