in my experience/understanding, clinics that want to cherry pick re. DE can do so by refusing to take some patients that might be harder to treat right out of the gate, by firing patients with too many failed cycles, & by refusing to offer shared risk cycles, which forces some patients to other clinics.
The 3rd one happened to me personally & I've heard of the 2nd one happening, including to a board buddy.
Usually it's the patients with repeat DE failures who end up seeing this side of things. We're in the minority as it is (which is good), but it means we also see a side of the business most never do.
I'm certain I saw things with my RE most of his patients never did, & it was not pretty.