This is correct. If you look at this Coleman pdf: http://www.coastdistribution.com/PDF...uct%20Page.pdf
...it shows ALL models available with a heat strip whether ducted or not. The difference is the control box in the upper unit and a different ADB (Air Distribution Box). I converted 4 Coleman Polar Cubs and 1 Coleman Mach III to have heat strips completely by the book. For most models of Coleman 13.5 units, you need an 8330B735 (65192) kit which is an ADB, Control Box and Heat Strip and runs roughly $160. For your thermostat you have a few options.
For all options, you will need another single wire run from your thermostat to your upper unit along with the other thermostat wires:
1) If your thermostat doesn't have a Heat setting on it, you need to purchase one that does.
2) You can purchase a thermostat that can control a furnace AND has an electric heat option.
3) If your thermostat already controls a furnace and you want it to continue to do so, you can add a second thermostat (like a cheap heat-only one from Home Depot) just to run the heat strip. I personally don't recommend this method as it will require some creative wiring in the upper unit so that the second thermostat will always run the blower.
4) If your thermostat already controls a furnace and you want to be able to switch between the heat strip and furnace, run your white heat wire from your thermostat through an on-off-on toggle switch with the thermostat wire going to the center pole, and your furnace and heat strip wires going to the opposing poles. I recommend this method as there can't be any conflict in the outgoing signal from the thermostat....it will run one or the other or nothing based on the toggle switch position.
I understand that running that extra wire can be an issue for some and don't really have any sound advice in that department. I was lucky in-that my thermostat wires running to my upper unit were not "attached" to anything along the way through the wall and ceiling. I was able to attach a strong string to my wires in the upper unit, pull the wires back through to the thermostat, attach the new white heat wire and re-pull it all back through with the string.