Velvet drive is one box that doesn't matter if it is turning or not. so seeing as fitting a shaft break is not so simple, allowing the box to spin freely is fine. It doesn't matter what gear
you are in as it is a Hydraulic box. If the front end of the box is nto turning, you have no oil
pressure and thus no cluthes engaged. So only the aft gear
is spinning. This is bathed in oil
so it is happy to spin freely.
Boxes that don't like being spun are usually because certain parts
are not bathed in oil and wear is a result.