If you're talking about the slide with your table and chairs in it, I can kinda see why they didnt put on on it. Like you said, they must figure its covered by the main awning.
IMO, I'd have one put on it. Reason being, storm rolls in, what do you do? Pull in the main awning. Now your slide is out there with no awning over it, unlike the others.
2017 North Point 375BHFS
2015 Silverado 3500HD Crew Dually Dmax 4x4