Seriously, reading the sports and then hitting the Shakespeare- what a nice “AND,” indeed. It can speak to willingness to go beyond the usual same old/same old/same as everyone else.
This is what worries: “scoffs at resume-padding activities–hence no fluff list of clubs, startups, volunteering, etc.” Fluff? There’s a balance required. And an awareness that activity choices are not just either/or: either “passions” or “padding.” They are experiences, contributions. Some for yourself (the kid who pursues ECs related to his future major or plays Ultimate Frisbee because he likes it.) Some for the group, meaning school and other,(not just sports.) And some because you see a need and are willing to commit (volunteering falls here.)
Still, if he really likes Yale, why not have him try? What other Early alternative would he go for, if not this? Just try to see if there are some other things he did that represent more than just what he “likes” and some idea anything else is fluff. Adcoms can’t guess that he’ll evolve when he arrives, they need to see it in how he chose, so far.
What I’d say? (What I did say to D2, when she applied ED somewhere.) “There are reasons they will like you. There may be things they think others do better. The final decision is out of our hands. But if it’s meaningful to you to try, go ahead, make your best decision.”