Add me to the list of people with same-day bookings that have gotten Pre. Also when you SDC you are reticketed and it goes through again (but same PNR, so maybe not..).
One time I had a ticket booked weeks in advance. Did OLCI to get my HOOU and no Pre banner, but also the hotel printer was screwed up so no HOOU. Checked in again on my phone - no banner. Went and got dinner, then afterward, repeated check-in on my phone and the new BP had the Pre banner. Decided to try for the HOOU again, so re-did OLCI and got both the Pre banner and my HOOU.
Moral of the story: it appears you can keep repeating OLCI and mobile check-in if your first attempt doesn't give you Precheck - though I wouldn't necessarily recommend doing this on a normal basis, DL IT being what it is.