Its in Barry Ernsts book. Though he said it took him 5 minutes to do all that running when he did a test run. In reality it takes more like 3 minutes. He mentioned the motorcycle radio issue in his book. He knew it damaged Adamss timeline of events. She said she was back inside the building within 5 minutes, but the motorcycle radio issue proves she was outside at least another 2 minutes.
I don't care what is in Barry Ernest' book. So what if it took her 7 instead of 5 minutes to return inside the building. It makes no difference whatsoever for the timeline.
She and Styles ran down the stairs after the third shot. The went down the stairs and next to the exit of the stairs on the left there is a loading door. They turned left and stepped on to the loading platform. They then needed to walk to the other side of the platform to go down the stars. From there they had to run back in the other direction towards the railway yard. There they are stopped by police and sent back. She then walks along side the building to get to the street in front of it. From there she walks to the front entrance of the building and overheared a radio report.
She didn't carry a stopwatch and it may well have been 7 minutes that she needed to get back into the building, via the loading dock at the back. Shelley and Lovelady estimated they returned to the building after 5 minutes, but that could easily also have been 7 minutes. That's when Adams saw Shelley and Lovelady.
This way the entire timeline fits and nobody needs to lie to the investigators, like they would have had to do in your foolish version of the events.