What I have from Carl’s training in 1988 was a 400m in 48 on 9/16 then practically nothing except rest and warmup until the first 100m heat on the 23rd.
In the past KK has posted about using a fast 400 to set up a race. In this case, we are talking about racing one or two 400s before the outdoor comp in the main event has really started. It’s a larger emphasis on endurance in the prep phase.