[eeverman@usgs.gov]

Looking at the docs for the types of dependencies, its more clear to me what is missing: Required overlap.

All of the relations specify that tasks *may* overlap, but do not require it. So essentially the types F-F and S-S should allow a 'In Unison' option, which would require that the tasks either start together or end together (with the option of an offset as is currently supported).

Some real world unison task examples:
* Start together: Fly Plane & Co-Pilot Plane
* Finish together: Cook Main Dish & Cook Side Dish to serve together.