There were changes to the loop positions between the 2019 and 2020 consultations. The original 2019 proposal had a four phase approach to the track work, with the last phase being a passing loop at Seaton Delaval station, this would have been somewhat shorter, at only 0.5 miles (0.8 km) , and designed primarily for looping freights, the station would have remained a single platform on the up side. They noted then that if late running of the service required passenger trains to cross there, then the down train would have to skip the call.
So by the 2020 consultation, for some reason they didn’t explicitly mention, the phased approach was dropped, and the loop was resited south, ie to what we are now calling Seghill loop, and is now significantly longer, at 1.5 miles, and no longer a potential problem for station calls.
Noting the points made by
@androdas about the series of tight bends, I noticed from a cab ride video taken a couple of months ago that just north of Seaton Delaval, at the first road bridge, the track seems to take the easiest curve through the opening, and there may not have been room there for two tracks without a much tighter curve, so maybe an additional bridge rebuild might have been needed there to get a decent line speed. I’m not sure if this video has been linked in this thread before. Time stamp is 10m 43s for the start of the Seaton Delaval to Redhouse Farm ‘curvy bit’…