Yes. The HQ, the base, sometimes some odd HQ-attached support (AAA guns or whatever). It may be - for me, anyway - that I would often want the HQ to move with the column, but the actual supply base, for example, to remain static where it is, out of harm's way. To achieve this now you will have to untick basing AND give a separate order to the base itself placing it to Defend wherever you want it to be. Once final positions are reached (if you need to reduce command load) you could then re-attach it to a Defend in situ order given to the main HQ, again, with basing unticked.
Basically, whatever the order, ticking 'basing' will invite the AI staff officers to find a suitable out-of-harm's-way location for HQ and base units and move them there (even if you used an in situ modifier).