That’s ridiculous. That’s like saying that Luffy wasn’t significantly stronger than Zoro in EL despite fighting someone that was near twice as strong as Zoro’s opponent because it was “situational.”
Zoro was full health post-medicine and Oda put him against King, while a worn Law and Kid are fighting Big Mom, who would murder King with ease. You’re right that it’s not an argument, but you’re wrong about for what. Zoro isn’t on their level, and never was. That was always fanboy stuff.