At least at our HS, LACs like Swarthmore are indeed tough admits, but it is not necessarily the exact same kids always getting into LACs like that and Ivies (obviously holding aside the recruited athletes). I think the conventional wisdom is the most selective LACs are maybe just a bit more into specific fit, and there is some evidence in SCOIR to suggest that (basically just that at least taken collectively, the most selective LACs seem to have a significant number of admits over a somewhat broader range of GPA/test combinations).
On the other hand, Chicago is considered even more like that, meaning they seem to have a specific type of fit they are looking for, and again the SCOIR data is “smeary” in a way that would support that hypothesis. So maybe the OP’s kid will just get into Chicago.
But if not, personally I would not rule out that they could get admitted to Swarthmore but not the Ivies remaining on their reach list. Nor would I guarantee it, and indeed it could be the opposite. I just think we would not find it surprising if there was a Swarthmore admit but not a Yale/Penn/Brown admit . . . for a kid who was as a really good fit.