The manual is wrong. I have to run a thermostat. If I don't, it won't get any temp in it.
Think about it. The longer the coolant stays in the block, the HOTTER it gets. If the radiator can't get rid of the heat, adding more heat only makes it worse.
Again, it's an ignorant old wives tale that coolant needs to stay in the radiator longer. The book is wrong.
Come to think of it, I can't think of a Chrysler book I have that says to keep the coolant in the radiator longer. It's just wrong and doesn't make sense. Just like multi pass radiators.