That makes sense in order to reduce the delays incurred. Which yard are they storing them in now? I know there's another yard on the right hand side as you head in the Sheffield direction, the sets having previously been stored on the left hand side. I think the other yard was full of coal wagons last time I went past over a year ago now. Presumably these have been moved and they are using that yard as additional storage?
I've seen a recent photo which shows the yard next to the Sheffield-bound line pretty full with a mixture of complete and incomplete 345's / 710's / 720's.
The fact that recent moves of off-lease sets have seen the loco run round in Doncaster then set off via Maltby means that the set has arrived at Worksop heading east, suggesting the mk4 sets are now being stored in the yard next to the Retford-bound line.