BA Seat maps within 24 hours of flight departure

Does BA withhold seat maps for flights departing within 24 hrs?
If so, why?
If not, then why the errors on BA 162 departing 5-Oct "There was an error message from the airline when trying to retrieve this seat map: 0102 SEAT MAP NOT AVAILABLE, REQUEST SEAT AT CHECK-IN" ...

I know that in general BA does not allow free seat assignments for non-elite passengers until within the 24 hr window before departure - however one of my uses of Expertflyer is always checking the seat map to see if there are better seats coming available due to upgrades, etc. I almost always check-in at the airport but get/change my seat assignments earlier.