Would that be one of those H&S or perhaps insurance things?
That's the only explanation I can think of, assuming its true of course.

Perhaps it's Skanska only when there's no steel supports maybe?
Or from when the supports started to be removed, since that's the moment when the risk situation would rise significantly. And of course, we don't know if all Atkinson's steel supports are to be removed (EH hinted some might be too risky) or indeed if it has been decided not to remove any of them.

But this is why the complete absence of official information is so unjustifiable. If the last phase of the project is ending up with Atkinson's supports not being taken out and no archaeological recording being done it is ending up very different to how it was presented and the taxpayers are entitled to be told.