Let's agree to disagree. My experience in relationships is that, no matter how small, these kinds of secrets aren't healthy in the beginning of a relationship. Women want to know if they have competition that act on their feelings so they can "deal with it", even if the guy isn't interested.
We will see how DPC will deal with this situation.
Men and women who date
do not want to learn about each others exploits. That's stupid, counter productive, and either is used for comedic and horror-story reasons, or will simply end in failure. Women do this with other women, and men with men to let off steam. Not to bond or tell your potential significant other how attractive you are. That's egotistical showboating that no one wants to hear.
And Sage always has competition. She's gorgeous.
MC always has competition! He is the MC, and his exploits have been known in merely a few months. Let alone the pictures around campus...
...but none of that matters because
they love each other.
Telling Sage about Zoey's confession is irrelevant, useless, and not important to either character, their relationship, or plot development. Via the phone call, Sage's concern for Zoey is over. It's unnecessary drama because you think "we should share everything" and "honesty is a big part of Sage's character."
If DPC wants melodrama, it could certainly happen. But it will just be a silly speed bump in the story. Now, the Jade issue actually impacts MC, and it makes little sense that he hasn't brought it up, when he is serious about Sage.
There is no "Zoey confession conflict" with Sage.