[yanks6621]

When OsO₄ adds to a double bound the OH must be on the same side. However will the bond rotate so that large groups that were on the double bound are furthest away?

F

[movies]

In an acyclic structure, that may happen, but that can't happen when you still have the double bond there.  Also, the rotation doesn't change the stereochemistry, it's just a different conformation of the molecule.

One other point, the rotation may be hindered by hydrogen bonding between the two alcohols!