Is there more than one ideal seat post height based on type of riding?
Yes.  However, it varies by type of riding and conditions.  All Mountain is probably the extreme example of this (and the main market for dropper seatposts).  All Mountain bikes are designed to be able to climb and for that generally one would want the seat in a "high" position to be efficient.  During a technical descent, however, the seat is generally preferred to be low and out of the way, useful for providing additional movement if necessary, but low enough to get behind for extreme braking.  

Other riding types may have only one "ideal" position.  Trials bikes, for example, will most often have no seat, since it is rarely used and only adds weight and gets in the way.  So there is an "ideal" position.  Most road disciplines generally have what is considered an ideal position and will not vary by riding conditions in that discipline.