You know, I hadn't paid enough attention to that distinction in the confirmation emails. I am glad I viewed this thread!
Day-before cancel time varies from 11:59PM to 6pm to 4pm among various properties = Hampton Inn to Doubletree to Embassy Suites to Hilton, etc. (I didn't check all past reservations) However, in only one case was it 24 hours prior to the stated check-in = 4pm to 4pm. Others varied widely from a 3pm check-in and 11:59pm cancel time, to 3pm check-in and 4pm cancel, to 3pm check-in and 6pm cancel, to 4pm check-in and 11:59pm cancel. Little consistency, so difficult to predict in advance.
(Conrad Maldives was 2pm checkin and cancel 4pm 30 days in advance, but that is an outlier)

But yes, it would certainly be helpful if that level of detail was included *in advance* when looking at prospective bookings. AND, even more so, if it was included when viewing existing reservations!!! (if the info is available to include in the confirmation email, it should be available to include in other places as well!)