This turns into a circular argument because he believes his intent to pursue other another relationship was so that he can meet the expectations she set.
Which is de facto true because he believes that he if she didn't set that expectation then he wouldn't do so.
Not to get too much into psychology, but not everyone has the same level of insight, and people often misrecognize or misattribute the motivations behind their actions. If his genuine belief that his motivations were what he stated then he cannot honestly answer the question any other way.
And yes, it seems stupid that he thinks that she wants him to make have a relationship with someone else so that she can feel more confident in the relationship. But that is what he understood that she was communicating and in fact the clarification of what her ask is was even more absurd.
Per Jakes testimonial
I did it because Madyln asked of these things
Not necessarily to go out and find someone and kiss them, but to make things real, and to make sure that my love for her isn't some fairy tale
some dreamy thing that she is Miss Perfection.
That's really the experience I was wanting to get out of this experience
To confirm my love for Madlyn. And that's exactly what I asked for
Her later clarification:
I just hate that you continue to say, like, "Make it real for me."
I didn't need you to, like, hook up with somebody.
Like that's not what I needed you to show me, that you could have, like, some sort of intimate physical connection with somebody else.
With us talking about marriage here, it was the fact that you were gonna be with somebody that's ready to get married, that is-- Could possibly even make you realize, "Shit, you know I could be with any number of women that can make me happy, that are ready to get married, that I don't have to chase or fight for."
It was real for me already.
I didn't need you to do anything else to make it real.
Jakes character per Madyln.
Colby has never talked to another woman like that.
He's never kissed another girl.
We don't even go out to clubs. And he did cut things off with her, he was like, "No, I am with Madyln." "I wanna be with Madlyn."
Cut things off before I found anything.
Here's the thing, Colby isn't on this show because he is unsure about Madlyn. He genuinely enmeshed with an emotionally abusive partner who communicated that she wanted him to pursue some sort of relationship so that after that experience she would be reassured. Knowing he's a super awkward dude who is not at all interested in pursuing other people.
Look at the patterns and characteristics of codependent people.
https://coda.org/meeting-materials/patterns-and-characteristics-2011/
Have you ever seen someone check so many boxes?
Madyln's insecurities sort of makes sense, she's so terrible to him. No wonder she is worried that one day he will snap out of it and leave.