Clarrification of optional rules -voluntary retreat of cavalry unit - must it be in command to utilize?

By Newman55f9, in Battles of Napoleon

Can an out of command cavalry unit voluntarily retreat when an enemy unit advances into an adjacent square?

Newman55f9 said:

Can an out of command cavalry unit voluntarily retreat when an enemy unit advances into an adjacent square?

I think they cannot. The rules say "Out of command units may not move" on page 27.

Even ssuming the unit group had a "Defense" order, if the unit was out of command it doesn't have the benefit of that order, so I'd agree that it is stuck standing its ground and cannot voluntary retreat.