In the case of a roas traffic collision where there is a liklihood of death after the collision due to injuries then yes, a collision will be treated as a crime scene until all available evidence is collected. Motorways have been closed for 24hrs in the past when evidence in particularly difficult scenes needed to be collected and vehicle actions reconstructed.
There are usually witness statements, differing accounts, pleas of amnesia etc etc. Where it is clear that a collision is caused by Driver A resulting in the deaths of Driver B then it doesnt take as long, as there is little crime scene / collision modelling to take place.
In this case, however, it is fairly clear cut; a two vehicle collision where Driver A doesnt phone signaller, puts vehicle on the crossing injudisciously and events play out.
If the statement came from suffolk police, I wouldnt put too much faith on their assertions... police statements are notoriously incorrect, as I see on an almost daily basis. Although given that most of tomorrow will be taken up with recovery perhaps, clearing of any hazardous effluent that may have been remaining in the vehicle and PW repairs possibly in to Thursday, then sure, it could very well be two days.