You are absolutely right about the manual there. The example that the manual uses there is a privately owned Transport Hub 1, which gives only 50 AP. You can see the icon for it on Page 127 and in the description there. 50 AP will only give you an optimal range of 50 AP, or 5 hexes on a dirt road. The manual shouldn't have used this as an example as it is pretty confusing. Most players will either build their own Truck Station or buy out the private option, which then upgrades it to Truck Station.
A Truck station, level 1, has an optimal range of 100 AP (Page 312). A dirt road logistical truck movement cost is 10 AP per hex (Page 156). So that gives you 10 hexes within optimal truck range at level 1 station. (Plus you can extend with supply base, of course.)
Your logistical problems went away--as mine did when I used to do the exact same thing as you do--but you are limiting your use of the resources. Your metal and IP and manpower costs will be higher. If several of these truck stations or supply bases are farther than five hexes from your city, you will start to get administrative strain. Plus, with the refocusing rule, a limit of four truck stations can extend the reach from your SHQ (the original station plus three extending the reach). If you limit yourself to 6 hexes between stations, that is a limit of 28 hexes long (6 for the first three, and then 10 after the fourth, regardless of any more truck stations). If you use 10 between stations your reach will be 40 hexes (and it might be a lot farther if you can use a supply base after each truck station, which I am not sure about).
If you are putting stations every 10 hexes and still seeing problems, it isn't the distance but the load--the truck station needs to be upgraded to handle all the resources, soldiers, and ammo being transported along it.