Many a school ends up overenrolled - I suppose that’s better for them than under enrollment - Purdue ever year, Bama, Tampa and many more I’m sure.
They don’t publish RD / ED rates but they have to be much lower - so it’s too much “risk” for them - because if you’re charging $60K a year (just for tuition), there’s sticker shock and many will see they can go elsewhere for less. If you tell a kid earlier they’re in and they’re excited, mentally they may have themselves there for months that it’s ingrained (like if they learn in December) vs. if they find out in March.
On the other hand, they use merit to make people think they’re special - but truth is they’re meeting a cost the market will bear (for top students).
If your student is qualified, I’d still have expectations - but you need to have reaches, matches and safeties - and you need to apply to “enough” schools. With Common app, it’s easier to apply to more schools - why so many apply to 20+.
As for ED, totally a personal call - and I’m like you - in part, because while I can afford full pay, I didn’t want to afford full pay.
There’s another chain where someone was rejected to Penn ED1 and now wants to do a polar opposite Tufts for ED2. The student is glad they were turned down ED1 to Penn realizing it wasn’t right. Well that could happen to anyone ED…so that’s a concern too.
You’ll have no issues (assuming you hit the target and safeties. Think about if the average kid is applying to 8-10 schools, the yield is 12.5% to 10%, etc. not sure of the exact # on average but it has to be in the 7-8 range I’d assume.