Disagree - someone paid an app fee and if they are offered a WL spot, they have every right to accept.
Every WL student (if the WL goes beyond May 1 or whatever the school’s deadline is this year), should have accepted a spot elsewhere.
If someone wants to see if they get into Harvard - then guess what - that’s their right. And like many who get offered admission off a WL, they’ll likely turn down the spot. I can’t imagine WL have high yields - because many kids will have moved on to #2, found a roomie, and fell in love.
Yes, some people are selfish. They paid and it’s their right. But guess what, if they have no intention of accepting a WL offer, the next person up will then get the offer.
If someone chooses to accept a spot, I say good for them - and I really wouldn’t give it too much thought.
And even in this instance noted by OP - you truly don’t know what this person you are referencing would do should they get offered a spot at a WL school.
There are things to worry about in life …but in my opinion, this isn’t one that should cause concern.