I agree, 2024 is stronger but is also more brittle and prone to cracking, 6062 is softer but way less likely to crack. This may be why they chose the 6062 for the application?
You have to be careful about that. 6061-T6 is more ductile than 2024-T3, which is more ductile than 7075-T6, but that doesn't mean that 6061 is less prone to failure/fracture/fatigue, it just means that it can likely take a repeated load at a higher percentage of it's strength for a given number of cycles. The higher strength alloy usually has better fatigue resistance/strength for a given STRESS, thus you never see primary structure or major fittings on commercial or military aircraft made from 6061, 6063 or other soft alloys; 2024 and especially 7075 are the order of the day, because the part can be made smaller/lighter.
The real reason for Vans using 6061 bar and angle for most of the bigger fittings is that 7075 and 2024 bar and especially angle is hard to find long lead time) and really expensive, it's just not worth the cost penalty to make the part from thinner 2024 or 7075 angle.
Just for giggles I looked at Aluminum, 1/8" thick, 1 inch leg angles on mcmaster. 6061-T6 is $3.22 a foot, 2024-T351 is $22 a foot, and 7075-T6 is $19 a foot. That's a very extreme price difference, but most of the systems fitings on RV's are analyzed by TLAR methods ("That looks about right") so there really isn't much benefit to using higher grade materials when you can't really justify making the part thinner because of lost stiffness or frankly, a flimsy appearance.
Edit; I looked at Mil-HDBK-5, the (outdated but still useful) bible of material properties for the aero industry. _Generally_ for 6061-T6, you'd expect a fatigue failure (in say, a round bar in tension) after 1M load cycles with a stress of 20,000 psi, with 7075-T6, you expect failure at the same number of cycles at 30,000 psi. So you should expect 7075-T6 to give equivalent service life at about 50% higher stress, that means (warning, math) you can use about 1/3 less material if using 7075 (in a strength limited part, some parts are designed primairly for stiffness not strength). Stress concentrations and things like non-room temp conditions might change that a little, but now you see why big $ airplanes are made from 7075, not 6061.
