You are almost correct, there are a couple of other factors that figure in.
The true problem is that there is not enough time for the PDS to do all the things required for a successful dispatch everyday. Yes they may fix it in one plan for one day, but it does not carry over into any other plans, you then have to copy it into every plan to make it work.
Lets not forget when you add or move an area from a route it changes Orion solution (sometimes) and you would have to either leave the parameters the same or change them. Last but not least..dynamic Orion....and you know what happens after that.
Enjoy your weekend.