Okay.. I've got an Electrical Engineering degree.. Guess I should use it once in awhile!
It can happen to any cord... but it is VERY rare...
All extension cords are engineered to assume that the cord will operate in open air and in a straight line. Now this of course isn't realistic, but they add margins of safety and most people never get close to the rated amperage of even a household cord.
I would not worry about this for your RV.
1) Your using it outside... So the cord has airflow (vs. someone who coils up an indoor cord under a rug)
2) The RV rarely draws the max amperage for any length of time. Maybe if you are running all the A/C units, cooking a roast for 3 hours and you leave the fireplace on?
3) Good luck getting an even/tight coil on your RV cord. Mine is fairly stiff no matter what the temp is outside.