For the record, Marita Koch did 10X400 in 65-70 with short rest. She did this as BASE TRAINING, before the real training starts. I've done the same kind of workout at the same period. In my case it was 12X400 with 60 sec in 66-68, right out of Johnny Mac's seminar notes.
The problem with a sprinter doing these types of workouts is they're not fast enough. This is jogging to a pure sprinter. Most sprinters these days in the fall are doing 3-6 X 300 in 37-38 as intensive tempo in 3 minutes or so.
One of Clyde Hart's 400m workouts is 4X350 in 49 with 5 min rest PLUS 8X100 fast hill runs PLUS 2X200 in 30 with 30 sec rest. Oh, and by the way, the day before that, they do 6X200 in 26 with 3 min.
Not only are these people slow, weak, lazy, and not willing to work very hard, they also don't know what the hell they're talking about. This ignorance goes all the way to the OP, which is letsrun.com thinking they actually know something. 30 minute runs for 400 meter and 400h training is not exactly unusual. Many coaches have this, including both Hart and Kersee, among many others. Clyde Hart encourages athletes to do 20 min jogs twice a week in the fall.