It was a satirical dig at the recent Arrowverse crossover event, when Green Arrow made Supergirl stay in the hangar during an alien invasion because angst.
Oh boy, there was plenty of questionable decisions in that crossover, for sure. I get swapping actors out because of fatigue (filming one episode of one show is hard enough already, nevermind 3 shows), but the backhanded explanations were often hard to swallow. "So-and-so supporting character decided to head home." You mean so and so who loves to battle? C'mon now.
I got that, but I just don't see the similarity in the situations.
There's no real similarity there but Old Mixer created the situation, for the sake of making a humorous scenario. Nothing more than a mere setup. No need to seriously compare/contrast.
What other franchise other than Marvel had a huge live-action superhero crossover with two dozen plus characters across multiple properties? The CW DC shows. That's the closest frame of reference we have. That's all the setup we need.