Yeah, that was amongst the hardest choices in the game thus far. On the one hand, Sage deserves to know what Chad did to her - it's hard to say it's not her secret when Chad (as far as we know) deliberately involved her the way he did. But on the other hand, Chad is clearly terrified of the secret getting out and being blindsided by it (rather than revealing it on his own terms) could be disastrous; plus it's not like we know the details of how their relationship started. But on the third hand, Chad being that far in the closet also means it's almost impossible he's ever going to tell Sage himself, which is what I would really like to happen; sadly, the MC is in no position to push Chad in that direction, so maybe telling Sage is the next best thing? On the fourth hand, however, even if Sage takes the news well it's by no means certain learning she was a beard will give her better closure than simply accepting Chad has moved on.
In the end, I generally looked for tie breaks based on a given playthrough. If I felt like I needed to be open and honest with Sage, or that I owed her one for helping Maya/Josy, I usually told her. If I didn't have that extra connection to Sage, I said nothing and hoped for the best.
I am very curious to see what comes of this. Hopefully it will be nuanced enough to have consequences both ways and not just be a 'gotcha' twist 2 episodes down the line.
Oh, and #FUCKYOUDAWE
As I said, this is a very strong argument. But we don't really know just why the relationship started. What if Sage inadvertently cornered Chad and he felt he had no option but to date her lest he give away his secret? Given the traditional connection between the HOTs and Tri-Alphas, it's possible dating the HOT president was expected of Chad. With him being (publicly) single and Sage obviously into him, maybe he couldn't think of a valid excuse that didn't call his sexuality into question.
Granted, it's still a miserable thing to do to someone, but now it's much less deliberate. This is why I wish we had the option to encourage Chad to come clean directly, but the MC is just not in a position where that is plausible (especially if he didn't defend Chad at the hearing).